alter session 简介

alter session set events 'immediate trace name heapdump level 2';

ALTER SESSION SET EVENTS 'immediate trace name LIBRARY_CACHE level LL';

其中LL代表Level级别,对于9.2.0及以后版本,不同Level含义如下:
Level =1 ,转储Library cache统计信息
Level =2 ,转储hash table概要
Level =4 ,转储Library cache对象，只包含基本信息
Level =8 ,转储Library cache对象，包含详细信息(包括child references,pin waiters等)
Level =16,增加heap sizes信息
Level =32,增加heap信息

alter system (session) set events 'immediate trace name controlf level 4' DUMP出控制文件

alter system (session) set events 'immediate trace name library_cache level 4' DUMP出LIBRARY

alter system (session) set events 'immediate trace name heapdump level 4' DUMP出share_pool

alter system (session) set events 'immediate trace name file_hdrs level 10'; DUMP出数据文件头

alter system set events 'immediate trace name systemdate level 4' 只能是SYSTEM

alter system dump datafile 2 block 88 DUMP出数据文件（只能是alter system）