Defining SETSYS parameters for aggregate backup

The SETSYS command allows you to externally define various aggregate backup environmental options.

The system programmer should include SETSYS commands in the DFSMShsm parmlib member (ARCCMDxx) to ensure that the settings are defined to DFSMShsm at startup initialization. If you are an authorized DFSMShsm user, you can issue the SETSYS command before an aggregate backup to modify the SETSYS parameters that control aggregate backup processing.

To specify how many ABACKUP commands can run concurrently, use the MAXABARSADDRESSSPACE parameter. MAXABARSADDRESSSPACE specifies the maximum number of concurrent ABARS secondary address spaces that DFSMShsm supports, up to 64. When determining the value to specify for MAXABARSADDRESSSPACE, you should factor in such items as system load, resource contention, and aggregate backup and recovery activity. The overriding factor is the number of tape drives available. Aggregate backup uses at least one tape drive for each address space and uses two if backing up user tape data sets or data sets residing on ML2 tape (the default for MAXABARSADDRESSSPACE is 1).
Note: When an ABACKUP command completes, ABARS will determine if there is another ABARS request queued that has not been processed. If there is, DFSMShsm will reuse the address space to process that command. The address space will remain active until there are no further ABARS commands queued, or the SETSYS MAXABARSADDRESSSPACE command has reduced the number of ABARS address spaces and this address space is no longer required.
Rule: If you issue two ABACKUP commands with the same aggregate group name, they cannot execute concurrently even if MAXABARSADDRESSSPACE is set to a value greater than 1.

The ABARSPROCNAME parameter specifies the procedure name that is used to start an ABARS secondary address space when no such address space is available for reuse.

The EXITON(exitname) parameter lets you specify which installation exits (ARCBEEXT, ARCEDEXT, ARCM2EXT, ARCTVEXT) are active during aggregate backup processing.

Each time you issue the ABACKUP command, an activity log is created. You can use the SETSYS ABARSACTLOGTYPE command to specify whether you want the ABACKUP activity log automatically written to SYSOUT or to DASD. You can use the SETSYS ABARSDELETEACTIVITY(Y | N) command to specify whether you want DFSMShsm to automatically delete the ABARS activity log that corresponds to the ABACKUP version being rolled off. The deletion occurs during ABARS roll-off processing or EXPIREBV ABARSVERSIONS processing, and removes the need to manually manage the ABARS activity logs.

You can use the SETSYS ABARSBUFFERS(n) command to specify the number of ABARS I/O buffers, up to a maximum of nine buffers. DFSMShsm multiplies the number you specify by two to determine the total number of buffers to use for I/O processing (one-half for input, one-half for output). If the number of buffers is not specified by the SETSYS ABARSBUFFERS command, a default setting of one is used.

Use the ABARSKIP(PPRC XRC) parameter on the SETSYS command to specify that you want the backup to skip level 0 data sets that are protected by the peer-to-peer remote copy function or by the extended remote copy function.

The SETSYS ABARSTAPES(STACK) command allows you to place (stack) the ABACKUP output files from a single aggregate group on a minimum number of tape cartridges (as few as one). The stacking function applies only to tape cartridges. Attempts to redirect ABACKUP output files to DASD when the STACK option is in effect causes ABACKUP to fail.

You can select which DFSMSdss messages should be written to the ABACKUP activity log by using the SETSYS ABARSACTLOGMSGLVL(FULL | REDUCED) command. If you specify SETSYS ABARSACTLOGMSGLVL(FULL), all DFSMSdss messages are intercepted and written to the ABACKUP activity log. If you specify SETSYS ABARSACTLOGMSGLVL(REDUCED), only the DFSMSdss messages ending in a “W” (warning messages) or “E” (error messages) are written to the ABACKUP activity log; no informational messages are written.

ABARS records the CPU time for processing ABACKUP requests, along with any applicable account code information. This information is written to the ABR record and can be obtained using the LIST AGGREGATE command. It is also written to the FSR control block. The FSR can be written as an SMF record if the installation specifies SETSYS SMF(smfid). ABARS then writes the FSR as smfid + 1 in the SYS1.MANx or SYS1.MANy system data sets. Installations can use the information to calculate charge backs for ABARS requests.

The SETSYS ABARSOPTIMIZE(n) command allows installations to adjust performance when invoking DFSMSdss to back up level 0 DASD data sets that are specified in an ABARS INCLUDE data set list. You can specify that DFSMSdss read one, two, or five tracks at a time, or one cylinder at a time. You can override the SETSYS ABARSOPTIMIZE value on an individual ABACKUP command by issuing the ABACKUP command with the OPTIMIZE(option) parameter.
Note: If the SETSYS DEBUG option is in effect when the ABACKUP command begins processing, DFSMShsm cannot move any data. The DEBUG option causes all ABACKUP commands to be processed as if the VERIFY option had been specified.

Related reading

Parent topic: Preparing for aggregate backup