When an Adaptive Server engine has no tasks to run, it loops, looking for executable tasks. The configuration parameter runnable process search count controls the number of times that Adaptive Server loops.
The default value of 2000 means that Adaptive Server loops 2000 times, looking for incoming client requests, completed disk I/Os, and new tasks in the run queue. If there is no activity for the duration of runnable process search count, and the engine has no outstanding (pending) disk I/O, then the engine relinquishes the CPU to the operating system.
If Adaptive Server uses a lot of system CPU, set the
system’s runnable process search count to
a lower value. However, since decreasing runnable process
search count increases latencies in responding to incoming
and outgoing network requests, decreasing this value may decrease
performance. The net effect depends on the amount of the server’s
workload in question.
The default for runnable process search count generally provides good response time, if the operating system is not running clients other than Adaptive Server.
Use sp_sysmon with other operating system monitoring tools to determine how runnable process search count affects Adaptive Server’s use of CPU cycles, engine yields to the operating system, and blocking network checks.
See Performance and Tuning Series: Monitoring Adaptive Server with sp_sysmon.
