Automatic addition of CPU virtual processors

When the database server starts, the number of CPU virtual processors (VPs) is automatically increased to half the number of CPU processors on the computer. This ratio of CPU processors to CPU VPs is a recommended minimum to ensure that the database server performs optimally in most situations.

During start up, the database server calculates a target number of CPU VPs that represents an even number equal to or greater than half the number of CPU processors and compares the target number with the currently allocated number of CPU VPs. The database server adds the necessary number of CPU VPs to equal the target number.

If fewer than eight CPU VPs are configured, the server can dynamically add CPU VPs to a total (configured plus added) of eight.

The SINGLE_CPU_VP configuration parameter must be set to 0 for CPU VPs to be automatically added. When CPU VPs are automatically added, the value of the VPCLASS configuration parameter is not updated in the onconfig file; therefore, the value of the VPCLASS configuration parameter for CPU VPs might not be the same as the actual number of configured CPU VPs.

Use the auto_tune_cpu_vps task in the Scheduler to control the automatic addition of CPU VPs. To prevent the automatic addition of CPU VPs, disable the auto_tune_cpu_vps task in the ph_task table in the sysadmin database:

UPDATE ph_task
  SET tk_enable = 'F'
WHERE tk_name = 'auto_tune_cpu_vps';