在一次测试中,需要模拟在归档模式下,数据库发生多次redo切换而这些redo并未被归档的情景,一般来说这样的情况只有在归档目录满的时候会遇到.但是在日常测试中,这样的归档目录满的模拟不太现实,可以通过oradebug SUSPEND来实现该功能,让arcn进程挂起
配置log_archive_max_processes为1(可以配置多个，但是1个更加方便测试)
SQL> show parameter log_archive_max_processes; NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ log_archive_max_processes integer 1
该配置可以在线修改,但是不重启数据库不一定完全生效(测试环境本来是4,修改为1之后,还有arc0和arc1进程)
查找arcn进程
[oracle@localhost trace]$ ps -ef|grep ora_arc oracle 3686 1 0 21:07 ? 00:00:00 ora_arc0_test
oradebug进程(session 1)
SQL> oradebug setospid 3686 Oracle pid: 57, Unix process pid: 3686, image: oracle@localhost.localdomain (ARC0) SQL> oradebug SUSPEND Statement processed.
alert日志
Tue Apr 16 21:09:42 2013 Unix process pid: 3686, image: oracle@localhost.localdomain (ARC0) flash frozen [ command #1 ]
切换日志(session 2)
SQL> archive log list;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 53
Next log sequence to archive 55
Current log sequence 55
SQL> alter system switch logfile;
System altered.
SQL> /
System altered.
SQL> alter system checkpoint;
System altered.
SQL> set lines 134
SQL> col member for a40
SQL> SELECT thread#,
2 a.sequence#,a.ARCHIVED,
3 a.group#,
4 TO_CHAR (first_change#, '9999999999999999') "SCN",
5 a.status,
6 MEMBER
7 FROM v$log a, v$logfile b
8 WHERE a.group# = B.GROUP#
9 ORDER BY a.sequence# DESC;
THREAD# SEQUENCE# ARC GROUP# SCN STATUS MEMBER
---------- ---------- --- ---------- ----------------- ---------------- ----------------------------
1 57 NO 3 261053 CURRENT /data/oracle/oradata/test/redo03.log
1 56 NO 2 261046 INACTIVE /data/oracle/oradata/test/redo02.log
1 55 NO 1 260856 INACTIVE /data/oracle/oradata/test/redo01.log
SQL> alter system switch logfile;--hang住
此时alert日志
Tue Apr 16 21:10:19 2013 Thread 1 advanced to log sequence 56 (LGWR switch) Current log# 2 seq# 56 mem# 0: /data/oracle/oradata/test/redo02.log Tue Apr 16 21:10:36 2013 Thread 1 advanced to log sequence 57 (LGWR switch) Current log# 3 seq# 57 mem# 0: /data/oracle/oradata/test/redo03.log Tue Apr 16 21:13:13 2013 ORACLE Instance test - Can not allocate log, archival required Thread 1 cannot allocate new log, sequence 58 All online logs needed archiving Current log# 3 seq# 57 mem# 0: /data/oracle/oradata/test/redo03.log
oradebug RESUME(session 1)
SQL> oradebug RESUME Statement processed.
alert日志
Tue Apr 16 21:14:23 2013 Unix process pid: 3686, image: oracle@localhost.localdomain (ARC0) resumed Archived Log entry 2 added for thread 1 sequence 55 ID 0x7dd4ccb7 dest 1: Archived Log entry 3 added for thread 1 sequence 56 ID 0x7dd4ccb7 dest 1:
hang住会话继续执行(session 2)
SQL> alter system switch logfile; System altered.
