Reference

This section contains a quick reference to the parameters, statistics, waits, and APT scripts mentioned in Chapter 3.

Parameters

Parameter

Description

_LATCH_WAIT_POSTING

Latch wait posting is a mechanism whereby a process can be woken (posted) when the latch that it requires becomes available.

If this parameter is set to 0, latch wait posting is disabled. If this parameter is set to 1 (the default), latch wait posting is enabled for the library cache and shared pool latches only. Any other setting results in latch wait posting being enabled for all latches.

_MAX_EXPONENTIAL_SLEEP

Consecutive sleeps during a single attempt to acquire a latch become progressively longer, under an exponential backoff algorithm, up to the limit specified by this parameter. Defaults to 200 centiseconds in Oracle8.

_MAX_SLEEP_HOLDING_LATCH

The maximum sleep allowed under the exponential backoff algorithm when the sleeping process is holding another latch. Defaults to 4 centiseconds.

_NO_PREEMPT

If this parameter is set to TRUE (the default) Oracle will use the operating system’s preemption control mechanism, if available, to minimize the risk of processes sleeping while holding a latch.

_SPIN_COUNT

The number of iterations to perform before sleeping when spinning to acquire a latch. Defaults to 1 on single CPU systems, and 2000 on multi-processor machines.

_SPIN_YIELD_CPU_FREQ

This parameter controls the frequency with which an Oracle process will offer to yield the CPU if possible ...

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