Synopsis

Values:1 to 1000000

Default:1

Specifies the number of times a process will request a latch until it successfully obtains one. Tuning this parameter can heighten performance in a multiprocessor environment. When the number of unsuccessful requests for a latch reaches SPIN_COUNT, the process sleeps, then tries to acquire the latch again. Since a latch is a low-level lock, a process does not hold it for long. Thus, the CPU time used by spinning a process is less expensive than that used by making a process sleep. The contention level of the latch can be monitored with the miss rate and sleep rate from the UTLBSTAT and UTLESTAT scripts. Try reducing the sleep rate by tuning the spin count. If the contention level is high, increase the spin count to allow processes to spin longer before acquiring latches. Because increasing the spin count increases CPU usage, however, system throughput may decline at some point. The default value is ordinarily sufficient for almost all systems.