Additional performance tuning recommendations

Tuning I/O

Because LOADPLUS reads and writes large amounts of data during typical load processing, one of the most important factors that affects LOADPLUS performance is I/O processing. To maximize I/O performance, LOADPLUS handles all of its own buffering, and performs I/O operations at the lowest level possible. This allows reading or writing of several blocks of data with each I/O operation and allows LOADPLUS to prefetch subsequent data.

In addition to the information in Performance-considerations-for-buffer-options and Performance-considerations-for-the-sort-processing-options, the following information can help you tune your I/O processing:

• Allocate input data sets with the largest block size possible to reduce the number of I/O operations that LOADPLUS requires to read the data set. LOADPLUS always calculates the optimum block size for output data sets.
• To avoid I/O queueing, allocate LOADPLUS data sets on separate channels and drives. If you do not have sufficient channels available, use separate drives and control units.

Providing maximum virtual storage

Because each task requires virtual storage for processing, LOADPLUS balances the multi-processing that it performs with the amount of virtual storage that it finds available. The primary use of virtual storage is for I/O buffers by either LOADPLUS or BMCSORT.

Because LOADPLUS uses as much virtual storage as needed, always specify as much virtual storage as you can. We recommend that you specify REGION=0M in your JOB or EXEC statement to tell the system to allocate all available virtual storage to the LOADPLUS job. If your data center does not permit you to specify REGION=0M, specify the amount that allows the most virtual storage both above and below the 16-megabyte line.

Using a region size that is less than optimal risks the following potential issues:

• Running less efficiently, which could result in additional CPU and elapsed time
• Encountering memory failures or jobs that fail when new versions implement changes that require additional memory

If you specify a value for REGION other than 0M, ensure that you have an appropriate value set for the MEMLIMIT parameter, either as your site’s default SMF option or on your JOB or EXEC statement. We make the following recommendations for the MEMLIMIT option:

• Specify NOLIMIT to allow unlimited above-the-bar memory.
• If you are unable to specify NOLIMIT, specify at least 4 GB; if you are loading LOB or XML data, specify at least 32 GB.