Performance considerations

This section explains how BMC AMI Copy syntax and installation options might affect performance.

Summary of performance notes

In addition to the steps outlined in this section, you might also want to review the warnings about the limitations of certain BMC AMI Copy features, incorrect usage of options and so on that are provided at appropriate places in this manual.

This section outlines some of the steps you can take to get the best possible performance with BMC AMI Copy:

• For full image copies:

  • If your backup strategy is to make full image copies only (no incremental copies), we recommend you always use FULL YES RESETMOD NO.

  • If your backup strategy is to make both full and incremental copies, we recommend the following suggestions to make full copies:

    • If you can make copies using SHRLEVEL REFERENCE, and can tolerate stopping the target spaces during the copy, use FULL YES RESETMOD YES. If you cannot tolerate stopping the spaces, use FULL YES RESETMOD NO.

    • If you cannot use SHRLEVEL REFERENCE or cannot tolerate stopping the target spaces, use FULL YES SHRLEVEL CHANGE RESETMOD NO or FULL YES SHRLEVEL CHANGE RESETMOD YES with option SLCHGRESET YES. Because you are using SHRLEVEL CHANGE, you could use QUIESCE AFTER to establish a good recovery point, if you anticipate that you might need to recover to a prior point-in-time. Alternatively, you could use BMC AMI Recover TIMESTAMP recovery to recover to a prior point-in-time.

  If you routinely back up your table spaces before applying updates in batch mode, using SHRLEVEL CONCURRENT enables you to make those copies while the updates are in progress (provided you have the Snapshot Feature installed and can make Snapshot Copies). Making Snapshot Copies in this situation narrows the batch window and provides you with SHRLEVEL REFERENCE copies in the event the batch update fails and a RECOVER TOCOPY is necessary.

• For incremental copies:

  • If your full image copies are made using RESETMOD YES, use FULL AUTO (or CHANGELIMIT or FULL NO) READTYPE AUTO and RESETMOD NO for your incremental copies.

  • If your full image copies are made using RESETMOD NO, use FULL NO READTYPE FULLSCAN and RESETMOD NO for your incremental copies.

  • If you want to make merged incremental copies, use CUMULATIVE YES. If you do not want to merge the copies, use CUMULATIVE NO.

  • If you use SHRLEVEL CHANGE, you can use QUIESCE AFTER to establish a good recovery point, if you anticipate that you might need to recover to a prior point-in-time.

• Copy an entire partitioned table space at once (assuming you have sufficient resources) by multitasking or by starting several jobs, each for a different partition (data set), and let these jobs run in parallel. This decreases the total elapsed time to copy either a partitioned table space or a table space that spans multiple data sets. Refer to DSNUM in COPY object options for information about copying partitioned data sets.

• Do not code DCB parameters for output data sets (specifically, BLKSIZE and LRECL) in your JCL. Let BMC AMI Copy choose the optimum values. If you choose to code a model DCB in your JCL, ensure that an optimal block size is specified.

• Use dynamic allocation of output copy data sets whenever possible.

• Ensure that your Db2 table spaces use cylinder allocation units.

• Ensure that any output data sets that are on DASD use cylinder allocation units.

• Allocate data sets, whenever possible, to have separate I/O channels to the Db2 table space and to each of the output data sets.

• Do not run RUNSTATS for BMCLGRNX. This results in the indexes for this table not being used and increases the time for the copy.

  Important

  BMCLGRNX table is not used with Db2 version 11 and later.