SINGLE_CPU_VP

onconfig.std value

0

range of values

0 = running with multiple CPU VPs
Any nonzero value = running with one CPU VP

takes effect

When the database server is shut down and restarted

refer to

Running on a single-processor computer, in the chapter on virtual processors in the IBM Informix Administrator's Guide

SINGLE_CPU_VP specifies whether or not the database server is running with only one CPU virtual processor.

Setting SINGLE_CPU_VP to nonzero allows the database server to use optimized code based on the knowledge that only one CPU virtual processor is running. It enables the database server to bypass many of the mutex calls that it must use when it runs multiple CPU virtual processors.

it is strongly recommended that you set this parameter when the database server will run only one CPU virtual processor. Depending on the application and workload, setting this parameter can improve performance by up to 10 percent.

If you set SINGLE_CPU_VP to nonzero and try to add a CPU virtual processor, you receive one of the following messages:

onmode: failed when trying to change the number of classname VPs by n.
onmode: failed when trying to change the number of cpu virtual processors by n.

If you set SINGLE_CPU_VP to nonzero and then attempt to bring up the database server with VPCLASS cpu,num set to a value greater than 1, you receive the following error message, and the database server initialization fails:

Cannot have SINGLE_CPU_VP non-zero and CPU VPs greater than 1.