SQL> select ksppinm,ksppdesc from x$ksppi where ksppinm like '%logging'; KSPPINM KSPPDESC -------------------- ------------------------------ _disable_logging Disable logging
因为特殊的需要,对这个参数进行了一点简单测试:
1.设置参数
[oracle@jumper bdump]$ sqlplus "/ as sysdba" SQL*Plus: Release 9.2.0.4.0 - Production on Wed Oct 19 11:01:19 2005 Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved. Connected to: Oracle9i Enterprise Edition Release 9.2.0.4.0 - Production With the Partitioning option JServer Release 9.2.0.4.0 - Production SQL> alter system set "_disable_logging"=true scope=both; System altered.
2.事务测试
SQL> create table t as select * from dba_users; Table created. SQL> select count(*) from t; COUNT(*) ---------- 12 SQL> shutdown abort; ORACLE instance shut down. SQL> startup ORACLE instance started. Total System Global Area 97588504 bytes Fixed Size 451864 bytes Variable Size 33554432 bytes Database Buffers 62914560 bytes Redo Buffers 667648 bytes Database mounted. Database opened. SQL> select count(*) from t; select count(*) from t * ERROR at line 1: ORA-00942: table or view does not exist
由于未产生相应日志,数据库crash或shutdown abort之后,上一次成功完成的检查点之后变化的数据将无法恢复。
3.观察alert文件
从日志中我们可以看到在instance recovery中,没有数据被恢复,只有成功完成的上次检查点之前数据可以被获取,之后数据都将丢失。
从日志中我们可以看到在instance recovery中,没有数据被恢复,只有成功完成的上次检查点之前数据可以被获取,之后数据都将丢失。
Wed Oct 19 20:38:38 2005 Beginning crash recovery of 1 threads Wed Oct 19 20:38:38 2005 Started first pass scan Wed Oct 19 20:38:39 2005 Completed first pass scan 0 redo blocks read, 0 data blocks need recovery Wed Oct 19 20:38:39 2005 Started recovery at Thread 1: logseq 2, block 201, scn 0.897632464 Recovery of Online Redo Log: Thread 1 Group 1 Seq 2 Reading mem 0 Mem# 0 errs 0: /opt/oracle/oradata/conner/redo01.log Wed Oct 19 20:38:39 2005 Completed redo application Wed Oct 19 20:38:39 2005 Ended recovery at Thread 1: logseq 2, block 201, scn 0.897652465 0 data blocks read, 0 data blocks written, 0 redo blocks read Crash recovery completed successfully