• 文档 215858.1 PURPOSE

This article explains how to use the HANGANALYZE utility to diagnose hanging issues in Oracle Databases.

本文解释了如何使用HANGANALYZE 以诊断Oracle数据中的hang问题。

• BACKGROUND

When a database has severe performance problems, the cause of the problem may be a HANG. Using trace files produced by HANGANALYZE, you will be able to quickly determine if two or more processes are deadlocked and how many other processes may be affected. By using HANGANALYZE, you may also determine if a performance analysis will be required to diagnose the real problem when a HANG is taking place.

当一个数据库发生严重性性能问题，问题的原因可能是HANG。使用Hanganalyze生成的trace文件，你将可以快速确定是否为两个进程发生死锁，涉及到多少个其他进程。通过使用HANGANALYZE，你也可以确定在HANG发生时是否需要进行性能诊断。

CONTENT

• WHY USING HANGANALYZE

A “true” hang in the Oracle database can be defined as an internal deadlock or a cyclical dependency between two or more processes. When dealing with DML locks (i.e., TM), Oracle is able to detect this dependency and rollback one of the processes to break the cyclical condition. On the other hand, when this situation happens with internal kernel-level resources (e.g latches or pins), Oracle is usually unable to automatically detect and resolve the deadlock.

在Oralce数据库中一个真正的hang可以定义为内部的死锁或者 多个进程间的循环依赖。当处理DML锁时，Oracle能都判断依赖关系并回滚其中一个进程来打破循环争用。另一方面，如果发生在内核层级争用，（如latch或pin），Oralce通常不能自动发现并处理死锁。

A severe performance problem may easily be mistaken for a hang. This usually happens when contention is so bad that it seems like the database is completely hung. Previous to HANGANALYZE (Available since Oracle realease 8.0.6), the only tool available to diagnose this type of problem was the well-known “SYSTEMSTATE dump”. A SYSTEMSTATE dump has the following disadvantages when dealing with hanging issues:

一个严重的性能很容易被误认为是HANG。这通常发生在争用非常严重，以至于看起来数据库完全hang住。在HANGANALYZE出现之前（8.0.6），诊断此类问题的工具是众所周知的 “SYSTEMSTATE 。

一个 “SYSTEMSTATE dump 在诊断一下问题时，存在不足。

SYSTEMSTATE dump reads the SGA in a “dirty” manner, so it may be inconsistent when the time to dump all the process is long.

SYSTEMSTATE dump 以脏读读取SGA，如果DUMP 所用进程需要很长时间，则可能会出现不一致的情况。

SYSTEMSTATE dump usually dumps a lot of information (most of which is not needed to determine the source of the hang), which makes difficult to determine the dependencies between processes quickly.

SYSTEMSTATE dump 收集大量信息（大部分在诊断hang时用不到） ，这将增加快速确定进城依赖关系的难度

SYSTEMSTATE dumps do not identify “interesting” processes on which to perform additional dumps (ERRORSTACK or PROCESS STATE).

SYSTEMSTATE dump 不能识别可疑进程，也就无法对这些进程进行额外的dump（ERRORSTACK 或PROCESS STATE）

HANGANALYZE use internal kernel calls to determine if a session is waiting for a resource, and reports the relationships between blockers and waiters. In addition, it determines which processes are “interesting” to be dumped, and may perform automatic PROCESSSTATE dumps and ERRORSTACKS on those processes, based on the level used while executing the HANGANALYZE.

HANGANALYZE 使用内核调用来判断一个session是否等待一个资源，并报告阻塞者和等待者。额外， 他将会判断哪些进程可疑，并可能自动对可疑进程进行PROCESSSTATE dump 与ERRORSTACKS，这依赖于执行HANGANALYZE的level。

Note: HANGANALYZE is not intented to replace a SYSTEMSTATE dump, but may serve as a road map to interpret a SYSTEMSTATE while diagnosing complex issues. HANGANALYZE 并不能替代SYSTEMSTATE DUMP，但是在诊断复杂问题时，可以作为SYSTEMSTATE 的路线图。 USING HANGANALYZE

The “HANGANALYZE” command is available since Oracle Release 8.1.6. In Oracle9i it was enhanced to provide “cluster wide” information in Real Application Cluster (RAC) environments on a single shot. The meaning of this is that it will generate information for all the sessions in the cluster regardless of the instance that issued the command.

HANGANALYZE在 Oracle 8.1.6.后可用。在Oracle 9i，在单一环境增加了集群信息，这意味着使用此命令可以跨越实例，收集集群所有sessoin的信息。

HANGANALYZE may be executed using the following syntax:

HANGANALYZE 可以使用以下语法执行

ALTER SESSION SET EVENTS ‘immediate trace name HANGANALYZE level ';

Or when logged in with the “SYSDBA” role,

或是使用SYSDBA角色

ORADEBUG hanganalyze

To perform cluster wide HANGANALYZE use the following syntax:

使用如下语法收集集群HANGANALYZE

ORADEBUG setmypid ORADEBUG setinst all ORADEBUG -g def hanganalyze

The sets the amount of additional information that will be extracted from the processes found by HANGANALYZE (ERROSTACK dump) based on the “STATE” of the node. See further detail in the “STATE DESCRIPTION” section of this document.

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