Considerations when loading a large number of partitions

Definition of a large number of partitions

Whether the number of partitions that you have is considered to be a large number depends on your environment. In the BMC testing environment, the following numbers are applied to LOADPLUS:

• For general recommendations described in this space, a large number of partitions was considered to be approximately 500 or more partitions.
• For copy recommendations, a large number of partitions was considered to be a total number of copy data sets (including local and remote copies) of approximately 1500 or more.

Recommended option values for loading a large number of partitions

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

• If you are replacing only a few partitions and all of the remaining partitions are empty, specify LOAD RESUME YES PART n REPLACE instead of LOAD REPLACE.
• Consider specifying REDEFINE NO, either in the installation options or on the LOAD command. This option creates additional data sets only when needed and cleans up unused data sets.
• If you are loading more than 2000 partitions, we recommend that you increase the value of your STOPRETRY installation option to a minimum of 450. Increasing this value can prevent your load job from failing while waiting for DB2 to stop the objects that are associated with the table space that you are loading.

• If you need to make copies, consider one of the following options to avoid encountering data set allocation restrictions of the operating system or LOADPLUS memory restrictions:

  • Limit the number of copies per partition.
  • If you are loading all partitions, specify COPYLVL FULL to create a single copy.
  • If you are loading a subset of contiguous partitions, create a single copy by specifying COPYSUBSET=YES in the installation options module and, if you are dynamically allocating copy data sets, COPYLVL FULL.

  For more information, see the COPYLVL option on COPYLVL or COPYLVL=FULL, and COPYSUBSET=NO.

  Important

  For partition-by-growth table spaces, these allocation and memory restrictions apply only when you are making inline copies and you also specify ORDER NO.

• If you dynamically allocate partition-level copies, LOADPLUS 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 copy data sets, change the value of the RECOVERYDDN command option (or RCVYDDN installation option) to specify a ddname; the prefix plus the highest partition number must not exceed eight characters.
• Ensure that the value of your LOCKROW installation option is YES.
• Consider using VOLCNT (AUTO, AUTO) instead of the default value of (25,25) to avoid data set allocation limitations.

Recommendations for avoiding constrained resources when loading a large number of partitions

When you are loading a large number of partitions, the potential for encountering constrained resources is greater than for other objects.

Use the following information to avoid or work around this situation:

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

Additional recommendations when loading a large number of partitions

If you are loading 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:

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

• BMCDICT

  If you are loading 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 (loading with LOADPLUS and reorganizing with REORG PLUS).