Oracle Internals: An Introduction

Reference

This section contains a quick reference to the parameters, events, statistics, and APT scripts mentioned in Chapter 2.

Parameters

Parameter	Description
_USE_VECTOR_POSTS	Vector posts enable multiple waiting processes to be posted in a single semaphore operation.
POST_WAIT_DEVICE	The post-wait driver is a pseudo device driver. Its functions are invoked when operations are performed against a device special file of that device type. Where this parameter is used, it specifies the path to the device file for the post-wait driver.
TIMED_STATISTICS	Should be set to TRUE whenever timing information may be required for tuning purposes, which is always.
USE_POST_WAIT_DRIVER	If this parameter exists, it should be set to TRUE in order to use the post-wait driver, instead of regular semaphore operations.

Events

Event

Description

10046

This is the event used to implement the DBMS_SUPPORT trace, which is a superset of Oracle’s SQL_TRACE facility. At level 4, bind calls are included in the trace output; at level 8, wait events are included, which is the default level for DBMS_SUPPORT; and at level 12, both binds and waits are included. See the excellent Oracle Note 39817.1 for a detailed explanation of the raw information in the trace file.

Statistics

Statistic	Source	Description
total_waits	V$SYSTEM_EVENT V$SYSTEM_EVENT	The number of distinct waits.
total_timeouts	V$SYSTEM_EVENT V$SESSION_EVENT	The number of waits that timed out instead of being posted.
logical_waits ...