Reorganizing a large number of partitions

Recommended option values for reorganizing a large number of partitions

Changing the following command or installation option values can improve the performance of your job and help avoid memory or other restrictions:

• If you need to make copies, consider one of the following options to avoid encountering data set allocation restrictions of the operating system or REORG PLUS memory restrictions:
  • Limit the number of copies per partition.
  • If your site’s recovery strategy allows for full copies, use one of the following options:
    • If you are reorganizing all partitions, create a single copy by specifying COPYLVL FULL.
    • If you are reorganizing a subset of partitions, create a single copy by specifying a single physically contiguous range of partitions, COPYSUBSET=YES in the installation options module, and COPYLVL FULL on your REORG command.
• If you dynamically allocate partition-level copies, REORG PLUS appends the partition number to the default ddname prefix. If you dynamically allocate partition-level copy data sets for more than 99 partitions, ensure that you change the value of the COPYDDN installation or command option to specify a ddname prefix; the prefix plus the highest partition number must not exceed eight characters. If you are also dynamically allocating remote copies, change the value of the RECOVERYDDN command option (or RCVYDDN installation option) to specify a ddname prefix for your remote copy data sets; the prefix plus the highest partition number must not exceed eight characters.
• Consider specifying REDEFINE NO, either in the installation options or on the REORG command. This option minimizes the time that REORG PLUS requires to delete and redefine the existing VSAM data sets for the table space or indexes.
• Ensure that the value of your LOCKROW installation option is YES.
• Consider using VOLCNT (AUTO, AUTO) rather than the default of 25 to avoid data set allocation limitations when 25 is excessive.

Avoiding constrained resources when reorganizing a large number of partitions

When you are reorganizing a large number of partitions, use the following information to avoid or work around constrained resources issues:

• Ensure that you have specified a region size that allows the system to allocate as much virtual storage as possible to the REORG PLUS job. We recommend that you specify REGION=0M in the JOB or EXEC statement of your execution JCL.
• If you have specified REGION=0M and your job fails with a constrained resources error, consider reorganizing fewer partitions in a single job.
• When you are reorganizing a large number of partitions and dynamic allocation is active, we recommend that you specify DYNAMNBR=1600 on the EXEC statement of your execution JCL. Including this parameter enables the system to acquire adequate resources immediately before their use and to release them immediately after use.
• Reorganizing a large number of compressed partitions might result in constrained resources. If you encounter this problem, consider specifying fewer partitions in a single job.

Additional recommendations when reorganizing a large number of partitions

If you are reorganizing a large number of partitions, you might need to increase the size of the following common utility table spaces from the standard size that was allocated during installation:

• BMCSYNC

  Estimate the allocation for this table space based on all of the following factors:

  • The number of utilities that you are running concurrently
  • The number of partitions that you are processing concurrently
  • The number of files that you are dynamically allocating

• BMCDICT

  If you are reorganizing compressed data, estimate the allocation for this table space by multiplying by 64 KB the number of compressed partitions that you are operating on concurrently.