oracle oradebug systemstate 是dba分析instance的重要方法，需要勤加练习、多多分析。
数据库版本
$sqlplus system/oracleoracle
SQL*Plus: Release 12.2.0.1.0 Production on Fri Apr 27 17:35:11 2018
Copyright (c) 1982, 2016, Oracle. All rights reserved.
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
SQL>
SQL> set lines 200;
SQL> set pages 200;
SQL>
SQL> select * from v$version;
BANNER CON_ID
-------------------------------------------------------------------------------- ----------
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production 0
PL/SQL Release 12.2.0.1.0 - Production 0
CORE 12.2.0.1.0 Production 0
TNS for Linux: Version 12.2.0.1.0 - Production 0
NLSRTL Version 12.2.0.1.0 - Production 0
SQL> 创建测试表，插入测试数据
SQL> create table tmp_peiyb_20180427 ( a varchar2(100),b varchar2(100));
Table created.
SQL> insert into tmp_peiyb_20180427(a,b) values('aa','bb');
1 row created.
SQL> commit;
Commit complete.
SQL>
SQL> session 1 更新，不commit
SQL> update tmp_peiyb_20180427 set b='cc' where a='aa';
1 row updated.
SQL> session 2 更新，会处于wait状态
SQL> update tmp_peiyb_20180427 set b='cc' where a='aa';
session 3 使用sys执行 oradebug systemstate
SQL> oradebug setmypid;
Statement processed.
SQL> oradebug unlimit;
Statement processed.
SQL> oradebug dump systemstate 266;
Statement processed.
SQL> oradebug TRACEFILE_NAME;
/u01/app/oracle/diag/rdbms/rac0/rac01/trace/rac01_ora_11369.trc
SQL>
SQL>
SQL>
SQL>
SQL> oradebug dump systemstate 266;
Statement processed.
SQL> oradebug TRACEFILE_NAME;
/u01/app/oracle/diag/rdbms/rac0/rac01/trace/rac01_ora_11369.trc
SQL> oradebug CLOSE_TRACE;
Statement processed.session 3 rac环境下使用sys执行 oradebug systemstate
SQL> oradebug setmypid;
Statement processed.
SQL> oradebug unlimit;
Statement processed.
SQL> oradebug setinst all;
Statement processed.
SQL> oradebug -g def dump systemstate 266;
Statement processed.
SQL> oradebug TRACEFILE_NAME;
/u01/app/oracle/diag/rdbms/rac0/rac01/trace/rac01_ora_13859.trc
SQL>
SQL>
SQL>
SQL>
SQL> oradebug CLOSE_TRACE;
Statement processed.无法登录数据库，需要添加 -prelim 参数
sqlplus -prelim / as sysdba;