第一章  Oracle hang 之sqlplus -prelim使用方法

很多情况下，Oracle hang导致sqlplus无法连接，从而无法获得Oracle系统和进程状态，使得定位问题缺少强有力的依据。所幸的是Oracle 10g推出了sqlplus -prelim选项，在Oracle挂起时依然能使用sqlplus，从而能获得数据库状态。
使用方法如下

引用

$ sqlplus -prelim "/as sysdba"

SQL*Plus: Release 10.2.0.4.0 - Production on Sun Mar 28 06:40:21 2010

Copyright (c) 1982, 2007, Oracle.  All Rights Reserved.

在prelim模式下，不可以查询数据字典,但可以关闭数据库

引用

SQL> select status from v$instance;
select status from v$instance
*
ERROR at line 1:
ORA-01012: not logged on

引用

SQL> shutdown abort
ORACLE instance shut down.

但可以使用oradebug，但对于系统诊断，已经足够了
dump系统状态

引用

SQL> oradebug setmypid                                            
Statement processed.
SQL> oradebug unlimit
Statement processed.
SQL> oradebug dump systemstate 266
Statement processed.

或者dump hanganalyze

引用

SQL> oradebug  hanganalyze 3
Hang Analysis in /oracle/app/oracle/admin/ora10g/udump/ora10g_ora_52642.trc

对于rac

引用

SQLPLUS> oradebug setmypid

SQLPLUS>oradebug setinst all

SQLPLUS>oradebug -g def hanganalyze 3

或者dump 进程状态

引用

SQL> oradebug dump processstate 10
Statement processed.

进一步，如果有10g客户端，数据库是9i，依然可以用-prelim

引用

$ sqlplus -prelim /nolog

SQL*Plus: Release 10.2.0.4.0 - Production on Sun Mar 28 06:50:19 2010

Copyright (c) 1982, 2007, Oracle.  All Rights Reserved.

SQL> conn sys/oracle@ora9i as sysdba
Prelim connection established
SQL>  oradebug setmypid
Statement processed.
SQL> oradebug unlimit
Statement processed.
SQL>  oradebug dump systemstate 266
Statement processed.

There are two ways to connect to sqlplus using a preliminary connection.

1. sqlplus -prelim / as sysdba

2. sqlplus /nolog
set _prelim on
connect / as sysdba

1. While running system state dump with "-prelim" option:

sqlplus -prelim / as sysdba

SQL*Plus: Release 10.2.0.2.0 - Production on Mon Dec 11 17:28:14 2006

SQL> oradebug setmypid
Statement processed.
SQL> oradebug unlimit
Statement processed.
SQL> oradebug dump systemstate 266
ORA-03113: end-of-file on communication channel
ORA-24323: value not allowed

2. The following error is reported in the alert.log:

ORA-07445: exception encountered: core dump [kgllkd()+1254] [SIGSEGV] [Address not mapped to
object] [0x000000030] [] []

The error did not crash background process or terminate the instance.

The issue is not resolved in any known patches.

Use any of the below workarounds:

· Connect / as sysdba (without -prelim)

OR

· Force the variable PGA to be initialized:

sqlplus -prelim '/ as sysdba'
oradebug setmypid
oradebug unlimit
oradebug call ksmcpg
oradebug dump systemstate 10

--测试环境11g,获lgwr的spid
SQL> select * from v$process where username='SYSTEM' and program like '%LGWR%';
 
ADDR                    PID SPID                     PNAME USERNAME           SERIAL# TERMINAL         PROGRAM                                                          TRACEID                                                                          TRACEFILE                                                                        BACKGROUND LATCHWAIT        LATCHSPIN        PGA_USED_MEM PGA_ALLOC_MEM PGA_FREEABLE_MEM PGA_MAX_MEM
---------------- ---------- ------------------------ ----- --------------- ---------- ---------------- ---------------------------------------------------------------- -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- ---------- ---------------- ---------------- ------------ ------------- ---------------- -----------
000007FF614CD768         11 17428                    LGWR  SYSTEM                   1 123-PC           ORACLE.EXE (LGWR)                                                                                                                                 d:\oracle11g_64bit\diag\rdbms\second\second\trace\second_lgwr_17428.trc          1                                                 5007762       5465314           131072     9921762

--另启一会话窗口,暂挂lgwr进程
SQL> oradebug setsospid 17428
ORA-00070: command setsospid is not valid
SQL> oradebug setospid 17428
Oracle pid: 11, Windows thread id: 17428, image: ORACLE.EXE (LGWR)
SQL> oradebug suspend
Statement processed.

--发生日志切换hang住
SQL> alter system switch logfile;
 
System altered
--新建一个会话窗口
create table t_h(a int);--语句hang住

--解挂lgwr进程,上述lgwr及create操作顺利执行完毕
SQL> oradebug resume
Statement processed.

小结：如果日志切换时,会暂住一切所有的数据库前端事务create and dml

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