Setting the MULTIPROCESSOR configuration parameter when using multiple CPU VPs

If you are running multiple CPU VPs, set the MULTIPROCESSOR configuration parameter to 1. When you set MULTIPROCESSOR to 1, the database server performs locking in a manner that is appropriate for a multiprocessor. Otherwise, set this parameter to 0.

The number of CPU VPs is used as a factor in determining the number of scan threads for a query. Queries perform best when the number of scan threads is a multiple (or factor) of the number of CPU VPs. Adding or removing a CPU VP can improve performance for a large query because it produces an equal distribution of scan threads among CPU VPs. For instance, if you have 6 CPU VPs and scan 10 table fragments, you might see a faster response time if you reduce the number of CPU VPs to 5, which divides evenly into 10. You can use onstat -g ath to monitor the number of scan threads per CPU VP or use onstat -g ses to focus on a particular session.


Copyright© 2019 HCL Technologies Limited