ANTXIN00 parmlib parameters

Parmlib parameters use syntax similar to that of TSO commands. Parameters consist of a category name, parameter names, and values. Table 1 provides a list of the possible parmlib parameters, as well as their associated XSET parameter, if applicable. XRC references static (S) parameters only once when the corresponding function is first invoked. XRC references dynamic (D) parameters continually each time the function is executed. The rightmost column lists the tuning tables' offset value that is associated with the parmlib parameter.

To determine the current settings for the parmlib parameter values, issue the XQUERY ENVIRONMENT(PARM) command. To find the default values for the parameters, issue the XQUERY ENVIRONMENT(PARM) command to an inactive or undefined session. The values displayed are from the control address space (ANTAS000). There are example output screens in Examples of XQUERY ENVIRONMENT reports. See XQUERY–Querying a session for more information on viewing environment settings.

BITMAP

XRC maintains two resynchronization bitmaps for each primary volume in a session, called n and n-1. The active bitmap is n, and the inactive bitmap is n-1. As an application program writes to a primary track, XRC records the change made by turning on a bit in the n bitmap. Periodically, the two bitmaps are switched in order to reduce the number of tracks that have to be copied in a recovery situation. The following parameters determine when the switching occurs.

ChangedTracks (RTRACKS)

Specifies the number of tracks that must change before the system data mover (SDM) switches the resynchronization bitmaps. You can specify a value from 0 to 99999. XRC does not use the number of changed tracks to determine whether to switch the bitmaps when the following conditions exist:

• The tracks value is set to zero
• The tracks value is set to a value that is greater than the number of tracks on a volume

DelayTime (RFREQUENCY)

Specifies how long the system data mover waits before it switches the resynchronization bitmaps. You can specify the frequency in hours, minutes, and seconds. You can specify a value between 00.00.30 (30 seconds) and 18.00.00 (18 hours). If you set the frequency value to zero (00.00.00), XRC does not use elapsed time to determine whether to switch the bitmaps.

Note:

1. The ChangedTracks and DelayTime parameters control how often the system data mover switches the resynchronization bitmaps. These parameters are triggers for the switch process based on either changed tracks or elapsed time. When the switch process is triggered, both time and track counters are reset. Each volume’s bitmap is reset individually and independently of other volumes starting from the time when the volume first started synchronization. This process tends to occur randomly for a number of volumes in any given interval.
2. In general, the defaults that are set for the ChangedTracks and DelayTime parameters work for most configurations. However, there might be benefits in decreasing these parameter values to minimize the amount of data that is transferred after returning from suspension. For instance, you would want to decrease the parameter values if:
   • You are running in an environment with a limited network configuration (and slower synchronization).
   • You are running in an environment with a high probability of short outages on the SDM connectivity.
3. When you set the ChangedTracks and DelayTime parameters, ensure that the settings do not refresh the volume bitmaps more than once every 5–10 minutes. For example, if the bitmaps are cleared at one minute intervals, significant subsystem and processor resources are used. Setting a higher value than the default for the ChangedTracks and DelayTime parameters can result in a longer volume resynchronization time. This is because it is likely that more data has changed on the primary volumes. Conversely, setting a lower value for these parameters can put a greater demand on the system data mover MIPS (for software bitmaps) or disk subsystem resources (for hardware bitmaps).
4. In an extremely large and active configuration, you might consider increasing the ChangedTracks value to a number greater than 7500; otherwise, switching might be performed too frequently. Also, when you are using a majority or mostly 3390-9 devices, the ChangedTracks option is more dominant.
5. For an extended outage, it is likely that the number of tracks updated during an outage are greater than those in the bitmap at the time of the outage. Therefore, the ChangedTracks and DelayTime parameters have less effect than for short outages. You must consider the expected length of an XRC outage when you evaluate the benefit that is gained from changing these parameter values versus the increased overhead.

CONTIME

This category of parameters is used by the ANTRQST API request of ILK=XRC XCONTIME to provide the session ID and High Level Qualifier values for accessing the dataset containing the session consistency time of volumes used by z/OS® System Logger.

Note: If the session_id is specified as ANTAS000 in the XSET command, the parmlib values are applied to the ANTAS000 address space and not to a specific session.

DefaultSessionID

Specifies the session id to be used in determining the master recoverable time for an XRC master session, or if a master session is not found, the consistency time for an XRC session through the XCONTIME API request. The session id must be the name specified on the MSESSION parameter of the XCOUPLE ADD request, or the session ID of a session specified on the XSTART command.

If an XRC session is coupled to a master session, specify the master session name to get the master recoverable time for the XRC session. If you specify the session id for a coupled session, the consistency time returned will be the data consistency time of the session if XRECOVER has not been executed against the XRC session.

DefaultHlq

Specifies the high level qualifier to be used in accessing the XRC master data set, or the state data set, to acquire the XRC consistency time through the XCONTIME API request. The hlq must be the hlq specified with the MSESSION parameter of the XCOUPLE ADD request (or default) or the hlq specified on the XSTART (or default) with the indicated session name on the DefaultSessionID parameter.

COUPLING

This category of parameters controls the coupling of multiple XRC sessions.

DatasetDelay

Specifies how often XRC reads from the master data set in a CXRC environment. If the XRC sessions are pacing each other, decrease this value. Based on the update activity level of the system, high-stress environments require a lower value than moderate-stress environments. You can set this value between 25 milliseconds and 250 milliseconds.

DeadSessionDelay

Specifies the time (in seconds) an active XRC session or set of active XRC sessions waits for a nonresponsive session, before suspending a session. This parameter applies to a CXRC environment. You can set a value between 10 and 120 seconds.

Some customers have found that increasing this value prevents a premature suspension of the session if an extended event occurs that can obstruct a single XRC session. If you are generating a dump of the XRC session, set this value to a higher value, such as 90 seconds.

DIAG

This category of parameters is used for diagnostics.

SCDumpType

Specifies the type of storage control dump to be taken for errors that result in state saves. Specify STATESAV for a storage control dump with warmstart (the default). Specify NDSS to request that a non-disruptive state save be taken, if the necessary level of microcode is present on the target controller.

IOTIMING

Normally, I/O is not timed. If it has not completed in an installation-defined amount of time (the missing interrupt handler (MIH) value), a warning message is issued to the operator console. This message states that a device interrupt might have been missed for the device. MVS periodically issues this message until either the I/O completes or is canceled. Because XRC is designed to monitor time on all of its I/O, it can tell the operating system it must cancel the operation. This occurs if an I/O operation has not completed in a specified amount of time.

The parameters that make up the IOTIMING XRC category control the timeout values for the XRC I/Os. If the XRC session initiates an I/O that fails to complete in the time specified in these fields, the I/Os end with a permanent error. A value of 0 in any of the following fields specifies no timing. If timing is used, the MIH is ignored for XRC I/Os.

InitializationReadWrite

Specifies the timeout values for the functions that read and write tracks during volume initialization. You can specify a value between 0 and 255. A value of 0 means that no timing is used.

MinExtenderRead

Specifies the minimum number of seconds that are used to time the I/O if XRC is reading record sets through channel extenders. You can specify a value between 0 and 255, where 0 indicates that the parameter must not be used. XRC ignores this parameter unless you set ShadowRead to 1.

MinLocalRead

Specifies the minimum number of seconds that are used to time the I/O if XRC is reading record sets locally. You can specify a value between 0 and 255. A value of 0 indicates that the parameter must not be used. XRC ignores this parameter unless you set ShadowRead to 1.

MiscHigh

Specifies the timeout value, in seconds, for volume initialization that performs the read of the hardware bitmap as well as other functions. You can specify a value between 0 and 255, where 0 indicates that the parameter must not be used. You may want to increase this value in a channel extender environment.

MiscLow

Specifies the timeout value, in seconds, for XQUERY I/O, among other things. You can specify a value between 0 and 255, where 0 indicates that the parameter must not be used. In a channel extender environment, increase this value to 10 seconds.

ShadowRead

Controls the read record set I/O time. The default value directs XRC to calculate the appropriate time based on the type of connection and the XSET TIMEOUT value specified. You can specify a value between 0 and 255 for the exact number of seconds to wait for the I/O to complete. If you specify 0, XRC does not use timing. If the value is set to 1, XRC uses the following method to determine the actual timeout value:

1. Find the minimum timeout value of all the storage disk subsystems. (See StorageControlTimeout under the SHADOW parameter.)
2. Find the maximum value from among the calculation from step 1, MinExtenderRead, and MinLocalRead.
3. Multiply the answer from step 2 by the ShadowTimeoutPercent value to get the number of seconds to wait.

If the I/O times out, XRC performs a test to determine if it is experiencing performance impacts—to determine if XRC is running out of data buffers, for example. If the answer is no, the I/O is issued again. If the answer is yes, XRC returns an error for the I/O.

ShadowWrite

Specifies the timeout value for writing updates to secondary volumes. A value of 0 indicates that the parameter is not used. You can specify a value between 0 to 255 seconds. If the value is 1, XRC uses the following method to determine the actual timeout value:

1. Find the minimum timeout value of all the storage disk subsystems. (See StorageControlTimeout under the SHADOW parameter.)
2. Multiply the answer from part 1 by the ShadowTimeoutPercent value to get the number of seconds to wait.

If the I/O times out, XRC performs a test to determine if it is experiencing performance impacts—to determine if XRC is running out of data buffers, for example. If the answer is no, the I/O is issued again. If the answer is yes, XRC returns an error for the I/O.

ShadowTimeoutPercent

Ensures that I/O times out before a storage control session timeout value is reached. This parameter specifies the percentage to use when XRC calculates read or write record set timeout values. (See the ShadowRead and ShadowWrite parameters.) You can specify a value between 10 and 90 percent.

MONITOR

XRC has a monitor task that periodically checks for delays in processing. If there are any delays, XRC issues message ANTX8117I. In addition, XRC can save the statistics that are used in making these determinations. XRC uses the value specified with the MonitorOutput parameter to tell if these statistics must be saved.

MonitorOutput

Specifies if the results of a monitor check must be saved. A value of ON routes the results to the MONITOR1 member of the state data set. A value of OFF directs XRC to not write the statistics.

MonitorWakeup

Specifies the delay time between collection of monitor statistics intervals in milliseconds. The default value is 10000 milliseconds (10 seconds). The range of valid values is between 5000 and 120000 milliseconds (5 seconds to 120 seconds).

If XRC sessions are coupled to a master session through a cluster, the MonitorWakeup value must be equivalent to the value specified for the cluster. If not, a message is issued warning that the cluster value is used for the XRC session.

NAMES

Values that are found in this category are only used when the XSTART command processes. To take effect, they must be in member ANTXIN00. If these values are found in any other member, they are ignored.

Hlq

Specifies the high-level qualifier for XRC data sets. The default is SYS1. This parameter is not applied unless it is in the ANTXIN00 member and is processed when the XSTART command processes. It can be temporarily overridden on the XADVANCE, XCOUPLE, and XRECOVER commands. It is permanently overridden on the XSTART command.

MHlq

Specifies the high-level qualifier for the XRC master data set. The default is SYS1. This parameter is not applied unless it is in the ANTXIN00 member and is processed at XSTART time. It can be temporarily overridden on the XCOUPLE, XEND, XQUERY, and XSUSPEND commands.

SHADOW

Shadowing (mirroring) is a main function of XRC. XRC takes a copy of data that is changed on a primary volume and writes it out to the corresponding secondary volume. You can specify the following parameters to control this process.

AllowEnhancedReader

Default value: NO

Specifies the use of the enhanced multiple reader function. Associated values are NO (the default) or YES.

• YES — enables the use of the enhanced multiple reader function if the required microcode features are available. Specifying YES allows you to activate the NumberReaderTasks parameter.

  If AllowEnhancedReader(YES) is specified, then to enable the enhanced multiple reader functions, do the following:

  1. Specify UTILITY(FIX) and RequireUtility(YES).
  2. Set the default value of MaxTotalReaderTasks to 32.
• NO — disables the use of the enhanced multiple reader function.

Note: If you do not suspend the volumes, you can not change the value from YES to NO for an active session . To disable the enhanced multiple reader function, see Disabling the XRC enhanced multiple reader functions for details.

ConsistencyGroupCombined

Default value: 5

Specifies a value that allows XRC to combine multiple consistency groups when data is written to secondary volumes. You can specify a value between 1 and 999. When using the XRC Multiple Reader function, use values of 5 or lower.

A high value can be advantageous if there is a secondary queue build up because combining consistency groups can result in increased parallelism when writing to the secondary volumes. This is beneficial if there are many volumes that are simultaneously being updated by application programs.

DeviceBlockingThreshold

Defines the number of record sets that must be in cache for a particular device before device blocking for that device is activated. The value can range from 0 to 255. A value of 0 instructs XRC to refrain from device blocking. The actual number of record sets used as a threshold value is the value of this parameter multiplied by 64.

DfltWritePacingLvl

Default value: 0

This value specifies the default session write pacing level to be applied to volumes that have explicitly been assigned the DVCBLOCK(WP0) attribute.

The write pacing level specifies the maximum level of write pacing that can be applied to the primary volume. The levels range from 1 (smallest) to F (largest injected pacing).

If nonzero, the value also applies to new volumes on write pacing-capable controllers that are added to the session without an explicit DONOTBLOCK or DVCBLOCK specification.

If you use the default or specify zero, the system enables volumes without DONOTBLOCK or DVCBLOCK specifications for device blocking. Also, if DVCBLOCK(WP0) is specified on the command, a zero value results in an XADDPAIR, or XSET error.

JournalPriority

Changes the dispatching priority for writing record sets to the journal. You can specify a value between 251 and 253. Higher values position the task earlier in the queue.

LowAttention

Specifies a low threshold value to be used by the storage control of the primary volume when XRC adds a volume pair. You can specify a value between 1 and 255 record sets. If the storage control session contains this number of record sets in cache, XRC raises an attention. This informs XRC that there are record sets that need to be read.

MaxBytesTransferred

Restricts the number of bytes that are written to secondary volumes by a single channel program. Generally, the IBM® ESS can write an unlimited amount of data in a single channel program. Older technology disk subsystems may experience secondary performance slowdown when writing large amounts of data in a single chain.

A value of 0 indicates that the amount of data that is written remains unrestricted. You can specify a value between 60000 and 9999999.

MaxTotalReaderTasks

Default value: If AllowEnhancedReader(NO) is specified, the default value is 40. If AllowEnhancedReader(YES) is specified, the default value is 32.

Controls the limit on the number of active LSS and SCID combinations in a XRC session. The value is 32-80. The parameter prevents the lack of buffer and inefficient processing caused by the excessive numbers of reader tasks. The ability to use a higher number is retained for the benefit of installations that might have more than 32 LSS and SCID combinations active in a session, but using higher numbers is not recommended.

If you increase the MaxTotalReaderTasks value, you can add new LSS/SCID combinations in an XRC session when issuing XADDPAIR commands. If the number of the active sessions is greater than or equal to the number of existing LSS/SCID combinations, you can decrease the value in MaxTotalReaderTasks. When the number of active sessions is less than the number of existing LSS and SCID combinations, you cannot decrease the value the MaxTotalReaderTasks. If you issue the XADDPAIR, the new value in the MaxTotalReaderTasks is used.

Note: If you change the value when XRC is inactive, and the new value is smaller than the number of LSS and SCID’s in the session, the XSTART command fails. To reduce the value below the amount used by the session, issue an XDELPAIR command to reduce the actual number of LSS/SCID combinations.

MaxTracksFormatted

Restricts the number of tracks being formatted in a single write record set channel program. A 0 value states that there are no restrictions. You can specify a value between zero and 999.

Note: XRC does not format tracks and update tracks in the same channel program.

MaxTracksRead

Specifies the maximum number of record sets that are read in a single channel program. The maximum number of record sets read in a single channel program is 246. For compatibility with previous releases, MaxTracksRead values between 1 and 255 are accepted, but any value above 246 is treated as equivalent to 246.

MaxTracksUpdated

Restricts the number of tracks being updated in a single write record set channel program. A zero value indicates that there are no restrictions. You can specify a value between zero and 999.

Note: XRC does not format tracks and update tracks in the same channel program.

NoTimeStampCount

Specifies the waiting period before XRC issues message ANTX8030W. If an application program writes to a primary volume, a copy of the changed data is saved in cache in a record set. At the beginning of a record set is a timestamp that indicates when the record set was created. Under certain circumstances, the timestamp might be zero. This parameter specifies the number of zero timestamps that are generated before message ANTX8030W is issued. You can specify a value between 0 and 99999. A value of 0 instructs XRC to not issue a message.

NumberReaderTasks

Specifies whether auxiliary readers are to be used and the number of the auxiliary readers. Each entry is a tuple. The first value is the SCSN value that the number of read tasks is set for. The second value is the number of read tasks to be used. The default value is (*,0). The default value means using the number of XRCUTL volumes to control the number of auxiliary readers, and applying the value to all SCSNs.

An asterisk (*) in the SCSN field inidicates that the number of tasks value must be applied. Refer to the following two examples:

• (AA, 8) indicates that you must set the number of read tasks for SCSESSION=AA to a value of eight.
• (*, 6) indicates set the number of read tasks for all SCSESSIONS to a value of six.

To enable the specification of NumberReadTasks, use either of the following ways:

• Issue an XADDPAIR command for a volume. The system uses the specifications of NumberReadTasks for each SCSN within each SSID during the XSTART of a new or inactive XRC session. If the new volumes are not added, the existing number of reader tasks might be increased or decreased by the specifications.
• Use the XSET session_id PARMLIB (member, ACTION(APPLY)) command for an active XRC session. You can activate the NumberReadTasks specification by using the PARMLIB to increase the number of reader. If all volumes in a SCSN on a SSID are suspended, you can only decrease the number of reader tasks.

PacingReportThreshold

Default value: 10 (milliseconds)

This value specifies the number of milliseconds of injected write pacing, per write I/O, that must exist for a write pacing-enabled volume to be flagged as "blocked" in XQUERY reports and XRC monitor data. Valid values are 0-255.

Note: When a write channel program creates several record sets, the maximum value is equal to the maximum value of pacing multiplied by the number of record sets created by the channel program. See Write pacing for details.

PavByteThreshold

Default value: 512500 (bytes)

Specifies the number of bytes used to determine when write I/O for a secondary device is to be split into multiple tasks. When the total number of secondary bytes in a consistency group for a given secondary device exceeds this value, XRC splits the I/O across the number of tasks specified in the PavVolumes parameter.

PavVolumes

Default value: 1

Specifies the number of parallel write I/O tasks to be used when PavBytesThreshold is exceeded for a given secondary device in a consistency group. Use values above 1 only when Parallel Access Volume aliases are available for the XRC secondary volumes.

ReadDelay

Specifies the frequency that XRC checks to see if there are record sets in cache. You can specify a value between 100 and 5000. The value is in milliseconds with a default of 1000 (one second).

You can attain the following results by changing the XRC parmlib to use a smaller SHADOW READDELAY value, such as 500:

• Achieve more aggressive Recovery Point Objective targets.
• Avoid delays from lightly loaded data movers in large scale configurations.

ReaderPacingLimit

Default value: 33 (percent)

Dynamically reduces the effective reader pacing window after "leading" readers have accumulated updates in the specified percentage of available data mover buffers. You can specify values between 20 and 65 percent. Higher values can increase data mover efficiency, but should be used only in environments where data mover buffers are plentiful. In cases where data mover buffers are tightly constrained, a value of 20 should be used.

ReaderPacingWindow

Default value: 3 (seconds)

Limits the extent to which the data mover can "read ahead" in a given session. Since data mover buffers are limited, "leading" readers that are keeping up with application updates must eventually wait for those "lagging" readers that are not keeping up.

This parameter specifies the number of seconds worth of updates that leading readers may accumulate in data mover buffers while waiting for lagging readers to catch up. The larger the pacing window value, the more efficiently the data mover can operate. You can specify values between 1 and 30 seconds, although values larger than 5 seconds should be used with care and only in situations where sparse updates are occurring and data mover buffers are plentiful. In cases where data mover buffers are tightly constrained, a value of 1 should be used.

Note that the use of an excessively large pacing window can lead to a data mover hang, allowing record sets to accumulate in cache with a potentially serious impact to Application I/O.

ReadRecordsPriority

Changes the dispatching priority for read record sets. You can specify a value between 251 and 253. Higher values position the task earlier in the queue.

RequireUtility

Default value: Yes

This parameter optionally prevents XADDPAIR of a non-XRCUTL when an active storage control session does not exist for the specified (or default) SCSESSION. Associated values are NO or YES (the default).

• YES — prevents XADDPAIR of a non-XRCUTL volume pair when an active storage control session does not exist for the specified (or default) SCSESSION.
• NO — enables XADDPAIR of a non-XRCUTL volume to proceed when an active storage control session does not exist.

ResidualLeftToRead

Specifies the smallest number of remaining record sets that causes XRC to perform another read. You can specify a value between 1 and 500 record sets.

Example: If you set the ResidualLeftToRead value to 50, and after reading record sets, there are only 40 record sets remaining, XRC does not read them. However, if you set the ResidualLeftToRead value to 50, and there are 50 or more record sets, then XRC issues another channel program to read the remaining record sets.

ScheduleVerify

Controls whether the data mover periodically schedules mirror status verification. The default value is NO.

StorageControlTimeout (TIMEOUT)

Specifies the primary storage control timeout value for application impact. The initial value is set when a storage control is installed. If XRC stops reading the session’s record sets, after the timeout value has elapsed, the session automatically terminates (for non-2105 disk subsystems) or suspends (2105 disk subsystems). You can specify a value in hh.mm.ss format between 00.00.00 and 18.00.00, where 00.00.00 uses the default value set during installation. When a storage control session initially starts, XRC uses the timeout value specified in the parameter. However, you can dynamically alter it using an XSET command. For more information about this option, see Using the XSET TIMEOUT parameter.

Non-2105 storage controls end their affected storage control sessions at the end of the specified TIMEOUT duration. XRC must then resynchronize all volumes in these sessions with a full-volume copy. 2105 storage controls suspend their affected storage control sessions and perform hardware bitmapping of changes to primary volumes. XRC does not need to perform a full-volume copy to resynchronize these volumes.

You can override the value specified with this parameter by issuing a timeout value with the XSUSPEND TIMEOUT command. The new timeout value remains in effect until you restart the XRC session.

SuspendOnLongBusy

Used to enable or disable Suspend on Long Busy function when a new storage control session is added.

If the storage control microcode supports the function, enabling will cause the microcode to automatically suspend the storage control session instead of raising extended long busy when sidefile limits are exceeded.

If the storage control microcode does not support the function, enabling will cause the data mover to suspend a storage control session as soon as it detects extended long busy due to sidefile exceeding limits. Storage control sessions that do not support suspension will be terminated.

Disabling allows the data mover to tolerate the long busy condition for 80% of the storage control session timeout interval, after which mirroring is suspended.

Note: Changing this value does not affect the attributes of existing storage control sessions. Use XSET with the SSID and SUSLBUSY keywords to change the Suspend on Long Busy attribute of existing storage control sessions.

UtilityDevice (UTILITY)

Specifies the method used for selecting a utility device. When you specify FIX, XRC uses the same primary volume. When you specify FLOAT, XRC dynamically picks the primary volume that has the lowest I/O activity.

VerifyInterval

Specifies the interval, in hours, between the scheduled verifications. The default value is 24 hours. A value of zero specifies that verification is performed during every monitor interval.

Note: Continual verification can degrade data mover performance. In production XRC environments, avoid specifying zero.

WriteRecordsPriority

Changes the dispatching priority for writing record sets to a secondary volume. You can specify a value between 251 and 253. Higher values position the task earlier in the queue.

WrtPacingResidualCnt

Default value: 80

This value is multiplied by 64 to determine a target device residual count, at which the maximum permissible pacing will be injected for a given write pacing-enabled volume. A value of 0 has the effect of disabling Write Pacing for a volume when it is next processed with XADDPAIR or XSET DVCBLOCK. Valid values are 0-255.

In general, larger values for this parameter will tend to give higher session delay times and less frequent pacing. Smaller values will tend to give lower session delay times and more frequent pacing.

WorkloadWritePacing

Default value: None

The values are as follows:

DISABLED

Workload-based write pacing should not be used

max-levels

For workload-based write pacing, specifies the maximum write pacing levels that can be applied to application system writes depending on the Workload Manager settings for the application's service class. max-levels consists of 6 values, 0-F, separated by commas or spaces. The values correspond to the available WLM settings for the Importance parameter, which has 5 levels and 1 discretionary value (the sixth number). The first value corresponds to WLM importance 1, the second value to importance 2, and so on. The values for WorkloadWritePacing must follow an ascending sequence, that is, each of the second through sixth values must be greater than or equal to the preceding entry, to ensure that high priority workloads (as indicated by a lower value for importance) are paced at a lower level than low priority workloads. Values that are equal to the preceding value in the list are accepted and act as a placeholder for importance levels that are unused at the application site. At least one of the 6 values must be non-zero.

If WorkloadWritePacing is not specified at XSTART, there is no default value. Instead, the WorkloadWritePacing values in effect before the session was suspended are used, or if WorkloadWritePacing was previously disabled, the value from volume-level write pacing parameters that were set on the XADDPAIR or XSET command are used.

To disable workload-based write pacing, you must specify WorkloadWritePacing(DISABLED). Removing the WorkloadWritePacing parameter does not cause XRC to revert to volume-level write pacing when the session is restarted with XSTART, or when you issue the XSET PARMLIB APPLY command. You can use the XSET PARMLIB APPLY command only to change the existing values for max-levels.

WorkloadWritePacing with max-levels cannot be specified with a value of 0 for WrtPacingResidualCnt.

For more information on write pacing levels, refer to the description of parameter DfltWritePacingLvl in this topic, and the DVCBLOCK parameter in XADDPAIR–Adding volume pairs or utility volumes.

For more information on workload-based write pacing, refer to Workload-based write pacing.

STARTUP

Use the values that are found in this category during the following functions:

• When you issue the XSTART command.
• When you start the MVS MODIFY operation of CREFRESH.
• During startup or restart of the XRC control address space (ANTAS000).
• When you issue the XADVANCE or XRECOVER command to start a cluster session.

Note:

1. If both NAMES and STARTUP are specified in ANTXIN00, and both have either 'HLQ' or 'MHLQ' parameters, then XRC uses the parameters specified under STARTUP.
2. You can change the parameters specified in the STARTUP category and then use the MVS MODIFY operation of CREFRESH. See Advanced Copy Services diagnostic aids for the syntax of this operation.

ClusterMSession

This parameter allows you to specify the XRC master session name to be associated with a cluster session. The msession id name is the logical session name used on the XCOUPLE command. A value of DISABLED (default) indicates that a cluster session is disabled for a logical partition. If something other than DISABLED is specified, all coupled XRC sessions in a logical partition are coupled to this specified master session through the cluster session.

To specify the XRC master session name, use the following guidelines:

• When you specify a single parameter, use the parameter name as the master session name on the logical partition to access to this parmlib.
• When you specify multiple parameters, specify the parameters in pairs. Each pair represents the system name of the LPAR and the master session name to be used in the LPAR. Use the system name as the first parameter of a pair. Use the master session name as the second parameter of a pair.
  Here is an example for lists of names: where System 1 represents the system name and msess1 the master session name for the first partition and System 2 represents the system name and msess2 the master session name for the second logical partition.

  ClusterMSession(System1 msess1-
                  System2 msess2)
                  

ClusterName

This parameter allows you to specify the XRC cluster session name to be used in a logical partition. This parameter is not applied unless it is in the ANTXIN00 member and is processed when the ANTAS000 address space is started or restarted and when the following MVS console command

F ANTAS000,CREFRESH

is processed. If no value is specified, the system name for the logical partition is used as the cluster session name (default).

To specify the XRC cluster session name, use the following guidelines:

• When you specify a single parameter, use the parameter name as the cluster session name on LPARs to access to this parmlib.
• When you specify multiple parameters, specify the parameters in pairs. Each pair represents an LPAR system name and the cluster session name to be used in the named LPAR. Use the system name as the first parameter of a pair. Use the cluster session name as the second parameter of a pair.
  Here is an example for lists of names: where System 1 represents the system name and cluster1 the cluster session name for the first partition and System 2 represents the system name and cluster2 the cluster session name for the second logical partition.

  ClusterName(System1 cluster1-
              System2 cluster2)
                  

Global

Specifies the data set member name containing XRC parmlib parameters which are applied to all XRC sessions when started using the XSTART command.

NOTE: XRC parmlib parameters also specified in the member specified on the Session parameter override the values specified in this Global member.

Hlq

Specifies the high-level qualifier for XRC data sets. The default is SYS1. This parameter is not applied unless it is in the ANTXIN00 member and is processed when the XSTART command processes. It can be temporarily overridden on the XADVANCE, XCOUPLE, and XRECOVER commands. It is permanently overridden on the XSTART command.

MaxControlTasks

This parameter enables you to control the number of tasks available in the ANTAS000 address space for the parallel processing of the following ANTRQST requests:

• ILK=XRC
• ILK=PPRC

The value ranges from 128 to 233. The default value is 128.

Note: GDPS/XRC and GDPS/PPRC installations must have at least one task available for each defined auto-operator.

MHlq

Specifies the high-level qualifier for the XRC master data set. The default is SYS1. This parameter is not applied unless it is in the ANTXIN00 member and is processed at XSTART time. It can be temporarily overridden on the XCOUPLE, XEND, XQUERY, and XSUSPEND commands.

OfflineDiscovery

Controls whether offline device discovery is performed during IPL when the ANTAS000 address space first starts up, and thereafter when ANTAS000 restarts after it has been canceled. A value of YES causes offline discovery to be performed. A value of NO bypasses offline device discovery. NO is the default.

Offline device discovery at IPL should be needed only if you are using one of the following:

• GDPS Metro/zGlobal Mirror (XRC) in HYPER-PPRC mode (Incremental Resynch)
• GDPS Metro/zGlobal Mirror under z/OS V2R1 with XRC offline primary devices.

Other XRC configurations or non-XRC environments do not directly benefit from offline device discovery at IPL. To avoid increasing overall IPL elapsed time unnecessarily, do not request offline device discovery unless it is required.

The value of OfflineDiscovery takes effect when the ANTAS000 address space is started during IPL, or with the automatic restart of ANTAS000 after it has been canceled. To activate a new value for OfflineDiscovery without an IPL, do the following:

1. Update the value in PARMLIB member ANTXIN00
2. Issue the system command CANCEL ANTAS000

The OfflineDiscovery keyword is ignored and is not processed if it is specified in the ALL or session member of hlq.XCOPY.PARMLIB.

Parmlib

Specifies which data sets to use when searching for members that contain parmlib parameters. A value of XCOPY (the default) indicates to XRC that it use hlq.XCOPY.PARMLIB. A value of SYS1 indicates to XRC that it use the MVS parmlib concatenation. If the parmlib concatenation is being used, messages that include the parameter library data set name display SYS1.PARMLIB+.

Session

This parameter allows you to specify groups of session id name and member name. The session id name is the logical session name used on the XSTART command, and the member name is the data set member name containing the parmlib parameters to be applied to the logical session when the session is started.

Note: The number of parameters specified with Session must be a multiple of 2 (for example, session_id name followed by member name). If multiples of 2 values are not specified, error message ANTI1031E is issued.

SuppressTimestamp

This parameter allows you to suppress channel program timestamping on XRC system data mover systems. A value of YES suppresses timestamping. A value of NO allows timestamping. If SuppressTimestamp is not specified, it is interpreted as SuppressTimestamp(NO).

You should suppress channel program timestamping if the XRC system data mover runs on a system that does not share a common time reference with the application systems that writes to the XRC primary volumes, to avoid the introduction of incorrect timestamps into the XRC storage control sessions.

The recommended use of this parameter is:

• SuppressTimestamp(NO) on application systems with a common time reference
• SuppressTimestamp(YES) on remote systems processing XRC, GDPS control systems (K-systems) and z/OS systems that have access to XRC primary volumes and do not share a common time reference with production systems.

Do not use SuppressTimestamp(YES) on application systems, as that would defeat the data consistency mechanism of XRC. SuppressTimestamp(YES) should be used only on systems that are not updating data or that do not have a common time reference, as a preventative measure to avoid incorrect adjustments to the XRC consistency time.

The value of SuppressTimestamp takes effect when the ANTAS000 address space is started during IPL, or with the automatic restart of ANTAS000 after it has been cancelled. To activate a new value for SuppressTimestamp without an IPL, do the following:

1. Update the value in PARMLIB
2. Issue this system command: CANCEL ANTAS000.

The value of SuppressTimestamp takes effect when the ANTAS000 address space is started during IPL, or with the automatic restart of ANTAS000 after it has been cancelled. To activate a new value for SuppressTimestamp without an IPL, do the following:

1. Update the value in PARMLIB
2. Issue this system command: CANCEL ANTAS000.

Refer to Recovery system clock considerations for more information.

zIIPEnable

This parameter specifies whether the ANTAS000, ANTAS0nn, and ANTCL0nn address spaces are enabled for running on zIIP processors. The values are:

FULL

The address spaces are enabled for running on zIIP processors. This option allows the maximum amount of XRC offload possible. The offloaded work will be visible in enclave reports.

YES

The address spaces are enabled for running on zIIP processors. This option allows non-I/O related XRC operations to be offloaded to zIIP processors.

NO

The address spaces are prevented from running on zIIP processors.

You can change the value dynamically for ANTAS0nn by changing the value and using the XSET command to activate the change. The new values apply to all newly created ANTAS0nn address spaces.

If you change the zIIPENABLE parameter, restart the XRC address spaces with these commands:

1. Either XSUSPEND TIMEOUT or XEND (according to your local procedures) to end ANTAS0nn address spaces
2. XSTART.

zIIPEnable is a global parameter, so the value contained in PARMLIB member ANTXIN00 is used at startup for all address spaces. Note that the zIIPEnable parameter is not processed if it is specified in the global member (specified with a member name of ALL in the global parameter) or in a session member. You can change the parameter dynamically by modifying the value, then using the XSET command to specify its location and activate the change. The updated value is applied to all newly created ANTAS0nn and ANTCL0nn address spaces and to any existing ANTAS0nn and ANTCL0nn address spaces that are restarted or that create new tasks.

Changes to this parameter are only recognized by XRC address spaces that are restarted after the change, or for which the XSET command is used to activate PARMLIB changes. The XQUERY ENVIRONMENT(PARM) command shows the current global setting. This setting may differ from the parameter in use by XRC address spaces that were not restarted and were not updated by the XSET command.

STORAGE

XRC uses virtual storage to process customer data. Use this parameter to define the amount of storage that is used in various operations.

The parameters include:

BuffersPerStorageControl

Specifies how many buffers XRC allocates per scsession specified. A value of 576 allocates 35 MB per unique scsession specified with the XADDPAIR command. Some customers have modified this field to a higher number to use the maximum number of buffers, even with a small number of sessions. You can specify a value between 100 and 25000 buffers.

PermanentFixedPages (PAGEFIX)

Specifies the maximum amount of real storage, in MB, that XRC keeps page fixed to process I/O operations. You can specify a value between 0 and 9999 MB. A value of 0 directs XRC to release fixed pages after they have been used.

Example: To minimize the processor load for two storage controls, you would set the PAGEFIX value to 70. The two storage controls divide the 70 MB to get 35 MB each, which is the maximum per storage control session. However, you must allocate 35 MB of storage for each unique scsession level that you initiate. If you have two primary storage controls and start two storage control sessions on each, you would set the PAGEFIX value to 140 MB of storage.

ReleaseFixedPages

Instructs XRC to release fixed pages. XRC tries to free up pages of storage that are not being used. For example, during heavy stress, a large number of buffers are pagefixed to hold the record sets that are being read from cache. Once the heavy demand has decreased, the pages that were fixed are freed if it is determined that the buffers are no longer needed. A value of NO instructs XRC to keep the pages, even if they are no longer needed. A value of YES instructs XRC to release pages that are no longer needed.

Note:

1. If you use ReleaseFixedPages(YES) and need to XDELPAIR all volumes for one or more sessions, IBM recommends that you suspend (throughXSUSPEND TIMEOUT) and restart the data mover session immediately after the XDELPAIR's have completed. Failure to do so can result in extensive storage fragmentation in the data mover address space, resulting in a subsequent inability of the data mover to obtain sufficient contiguous storage for XADDPAIR, XQUERY, and other processes.
2. The number of pages kept fixed for an extended period of time does not exceed the value specified in the PermanentFixedPages parameter.

TotalBuffers

Controls the maximum number of buffers used for an XRC session. Some customers have used a lower value to limit the amount of real storage that is used for an XRC session. You can specify a value between 100 and 25000 buffers.

Lower this value to a level that allows all the buffers to be pagefixed when the system has insufficient real storage to pagefix all of the allocated buffers. Lowering this value might improve performance. It may also reduce processor usage as long as the lower value does not introduce significant performance problems caused by the smaller number of buffers as a working set.

If you apply a PARMLIB change to an active session that decreases the number of buffers available, excess buffers will be freed immediately. This occurs even when RELEASEFIXEDPAGES (NO) is currently in effect. IBM recommends that you make such changes during periods of light workload. Making the change during a heavy workload period may adversely impact session performance.

If you apply a change that increases the number of buffers available, the new buffers are allocated the next time the data mover encounters a data shortage.

Note: This is not an absolute limit on the storage that will be used for buffers in an XRC session.

IODataAreas

Specifies the real storage allocation for XRC channel programs and work areas that are associated with I/O operations. A value of 256 is best for installations that have less than 256 volumes. You can specify a value between 100 and 9999.

VOLINIT

Volume synchronization and resynchronization is the process of copying data from a primary volume to the secondary volume with which it has been associated. The following parameters help control this process.

EnableRefreshs (REFRESHS)

Indicates whether the TSO XSET REFRESHS command is enabled for execution. The default is NO, disabling the REFRESHS command. EnableRefreshs requires a YES value to enable the XSET REFRESHS function. See the REFRESHS parameter description for more information.

InitializationMethod (COPY)

Specifies the extent to which the primary volume is copied to the secondary volume. Specify FULL if the complete primary volume is to be copied to the secondary volume. If only the allocated space on the primary volume is to be copied, specify QUICK. At the beginning of a quick copy operation, XRC performs a reserve against the VTOC of the primary volume to get the allocated extents. After XRC determines the allocated extents, it releases the reserve. For more information about these options, see Adding a volume with the FULLCOPY or QUICKCOPY option.

Note: To ensure data integrity, the initial processing for QUICKCOPY must issue a reserve and then a release for the primary volume. This must be done during the initial phase of the synchronization process. If access to the primary volume is through a channel extender and the connection fails while XRC has the volume reserved, applications at the primary site are not able to access the primary volume.

InitializationsPerPrimary (SCSYNCH primary)

Specifies the maximum number of primary volume synchronizations and resynchronizations that can occur concurrently on a single storage control. You can specify a value between 0 and 45. A value of 0 stops the selection process but processing of existing volume synchronization and resynchronization tasks continues.

InitializationsPerSecondary (SCSYNCH secondary)

Specifies the maximum number of secondary volume synchronizations and resynchronizations that can occur concurrently on a single storage control. You can specify a value between 0 and 45. A value of 0 stops the selection process but processing of existing volume synchronization and resynchronization tasks continues.

HaltAnyInit

Pauses volume initialization if the record set residual count rises above the HaltThreshold value on any storage control, rather than just the storage control with which the primary volume is associated. A YES value allows pausing of any storage control. A NO value allows pausing for only the primary volume storage control.

HaltThreshold

Stops volume synchronizations or resynchronizations if the record set residual count of the storage control associated with a volume reaches this threshold value. A low value reduces the impact of volume initialization activity that is running concurrently with heavy update activity. If this threshold is reached, volume initialization pauses until the residual count drops below the threshold. When the residual count drops below the HaltThreshold value, the volume synchronizations or resynchronizations begin again. You can specify a value between 0 and 65535. A value of 0 stops all volume synchronizations or resynchronizations regardless of Ioad or IO activity.

MaxNumberInitializations (SYNCH)

Specifies the number of volume synchronizations and resynchronizations that can occur simultaneously in an XRC session. You can specify a value between 0 and 45. A value of 0 stops the selection process, but continues processing existing volume synchronization and resynchronization tasks.

MaxNumberInitializations specifies an XRC session-level value. For each synchronization task that it starts, XRC fixes real page storage that is based on the following formula:

{MaxNumberInitializations*(number of pairs in CPY status)*360K}

This storage is in addition to the real storage that is used by normal update processing. The real storage remains pagefixed for the total time the volumes are being synchronized or resynchronized.

SelectionAlgorithm (PRIORITY)

Specifies the method the system data mover should use when choosing the next volume pair to be synchronized or resynchronized.

FIFO

Choose volumes in the order that they were added with the XADDPAIR command

LOAD

Choose volumes whose primary storage controls have the least load. XRC considers a primary storage control to be overloaded if it has a higher number of record sets than the value set for the HaltThreshold parameter. LOAD is the default.

XRC bypasses a volume pair if the primary storage control is overloaded. If bypassed, the volume remains the next eligible candidate for XRC to select when the load decreases.

SIZE

Choose volumes based on the total number of cylinders, from largest to smallest. The parameters MaxNumberInitializations, InitializationsPerPrimary and InitializationsPerSecondary are honored; in addition, to avoid overloading storage control sessions, SIZE causes the system data mover to choose the volume with largest number of cylinders on the controller with the least residual load. If there are multiple volumes with the same number of cylinders on controllers with the same residual load, the volume that was XADDed first is processed next.

TracksPerRead

Specifies the number of tracks to be read in a single Read Track channel program. You can specify a value between 1 and 15 tracks.

TracksPerWrite

Specifies the number of tracks to be written in a single Write Track channel program. You can specify a value between 1 and 15 tracks.

SecondaryDeviceRange

Specifies whether a secondary device range filter should be used and if so, the list of device ranges to use. The filter is applied to the secondary device in an XADDPAIR command. If the secondary device number is not within one of the specified ranges, the XADDPAIR command will fail.

Each range contains two four-digit hexadecimal numbers separated by a colon. The value to the left of each colon must be less than or equal to the value to the right of the respective colon. If both values in the range are the same, a filter will be created for the single specified device number. Values with less than four digits are right justified and padded with zeroes. The list of ranges may be separated by commas or blanks. There can be up to 256 ranges in the list.

If SecondaryDeviceRange (NONE) is issued, the list of secondary device ranges will be cleared. If any other device range values are listed along with value 'NONE', the command will fail. Here are a few examples:

• (0F50:0F5F, 0F70:0F7F) means to create secondary device range filters for ranges 0F50 to 0F5F and 0F70 to 0F7F.
• (F5F:F5F F86:F86) means to create secondary device range filters for device number 0F5F and device number 0F86.
• (NONE) means to not use any secondary device range filters.

Once a SecondaryDeviceRange value has been applied, the filter will be used for all subsequent XADDPAIR commands.

The default value is 'NONE'. The default value means that no secondary device range filters will be used when processing an XADDPAIR command.

SecondaryVolserPattern

Specifies whether a secondary VOLSER pattern filter should be used and if so, the list of VOLSER patterns to use. The filter is applied to the secondary device in the XADDPAIR command. If the secondary VOLSER does not match one of the specified VOLSER patterns, the XADDPAIR command will fail.

Each pattern contains a six-character or smaller value with valid characters being those characters which are valid to appear in a VOLSER plus a single-character wildcard '%'. Each pattern must contain at least one single-character wildcard. Lower case is converted to upper case prior to comparison. The list may be separated by commas or blanks. There can be up to 256 patterns in the list.

If SecondaryvolserPattern (NONE) is issued, the list of VOLSER patterns will be cleared. If any other VOLSER values are listed along with value 'NONE', the command will fail. Here are a few examples:

• (X%%%%%) means to create a secondary VOLSER pattern filter for pattern X%%%%%. Acceptable VOLSERs must have an 'X' as the first character and must be one to six characters in length.
• (%%B %) means to create a secondary VOLSER pattern filter for patterns %%B and %. Acceptable VOLSERs must be three characters in length with the third character of 'B', or they must be one character in length.
• (S%S%%%,S%N%%%) means to create a secondary VOLSER pattern filter for patterns S%S%%% and S%N%%%. Acceptable VOLSERs must have an 'S' as the first character, an 'S' or 'N' as the third character, and must be three to six characters in length.
• (NONE) means to not use any secondary VOLSER pattern filter.

Once a SecondaryVolserPattern value has been applied, the filter will be used for all subsequent XADDPAIR commands.

The default value is 'NONE'. The default value means that no secondary VOLSER pattern filters will be used when processing an XADDPAIR command.

Note: If both SecondaryDeviceRange and SecondaryVolserPattern are specified, the device number comparison is performed first with an XADDPAIR command. Therefore if the device number isn't found within any of the specified ranges, the XADDPAIR will fail regardless of whether or not the VOLSER matches a VOLSER pattern.