删除Oracle Online Redo 测试SQL> select * from v$log;? GROUP# THREAD# SEQUENCE# BYTES BLOCKSIZE MEMBERS ARC STATUS---------- ---------- ---------- ---------- ---------- ---------- --- -------- 1 1 4 52428800 512 1 NO CURRENT 2 1 2 52428800 512 1 NO INACTIVE 3 1 3 52428800 512 1 NO INACTIVE删除在线日志SQL> !rm -rf /u01/app/oracle/oradata/orcl11g/redo0*?SQL> !ls -l /u01/app/oracle/oradata/orcl11g/redo0*ls: cannot access /u01/app/oracle/oradata/orcl11g/redo0*: No such file or directory?SQL> quitDisconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit ProductionWith the Partitioning, OLAP, Data Mining and Real Application Testing options[oracle@cym1 trace]$ ll /u01/app/oracle/oradata/orcl11g/redo*ls: cannot access /u01/app/oracle/oradata/orcl11g/redo*: No such file or directory查看删除日志后对数据库操作的影响：SQL> alter system switch logfile;?System altered.?SQL> /?System altered.?....SQL> select * from v$log;? GROUP# THREAD# SEQUENCE# BYTES BLOCKSIZE MEMBERS ARC STATUS ---------- ---------- ---------- ---------- ---------- ---------- --- ---------------- 1 1 10 52428800 512 1 NO INACTIVE 2 1 11 52428800 512 1 NO INACTIVE 3 1 12 52428800 512 1 NO CURRENT ?SQL> select * from v$logfile;? GROUP# STATUS TYPE MEMBER IS_---------- ------- ------- -------------------------------------------------- --- 2 ONLINE /u01/app/oracle/oradata/orcl11g/redo02.log NO 3 ONLINE /u01/app/oracle/oradata/orcl11g/redo03.log NO 1 ONLINE /u01/app/oracle/oradata/orcl11g/redo01.log NO??SQL> alter system switch logfile;?System altered.?SQL> alter system switch logfile;?System altered.?SQL> select * from v$log;? GROUP# THREAD# SEQUENCE# BYTES BLOCKSIZE MEMBERS ARC STATUS ---------- ---------- ---------- ---------- ---------- ---------- --- --------------- 1 1 13 52428800 512 1 NO INACTIVE 2 1 14 52428800 512 1 NO CURRENT 3 1 12 52428800 512 1 NO INACTIVE ?可见删除在线日志不影响数据库正常操作。对数据库启动关闭的影响：SQL> shutdown immediate;Database closed.Database dismounted.ORACLE instance shut down.SQL> startup nomount;ORACLE instance started.?Total System Global Area 409194496 bytesFixed Size 2253744 bytesVariable Size 310381648 bytesDatabase Buffers 92274688 bytesRedo Buffers 4284416 bytesSQL> alter database mount;?Database altered.?SQL> alter database open;alter database open*ERROR at line 1:ORA-03113: end-of-file on communication channelProcess ID: 76747Session ID: 1 Serial number: 3?--查看日志alter database openErrors in file /u01/app/oracle/diag/rdbms/orcl11g/orcl11g/trace/orcl11g_lgwr_76732.trc:ORA-00313: open failed for members of log group 1 of thread 1ORA-00312: online log 1 thread 1: ‘/u01/app/oracle/oradata/orcl11g/redo01.log‘ORA-27037: unable to obtain file statusLinux-x86_64 Error: 2: No such file or directoryAdditional information: 3Errors in file /u01/app/oracle/diag/rdbms/orcl11g/orcl11g/trace/orcl11g_lgwr_76732.trc:ORA-00313: open failed for members of log group 1 of thread 1ORA-00312: online log 1 thread 1: ‘/u01/app/oracle/oradata/orcl11g/redo01.log‘ORA-27037: unable to obtain file statusLinux-x86_64 Error: 2: No such file or directoryAdditional information: 3Errors in file /u01/app/oracle/diag/rdbms/orcl11g/orcl11g/trace/orcl11g_ora_76747.trc:ORA-00313: open failed for members of log group 1 of thread ORA-00312: online log 1 thread 1: ‘/u01/app/oracle/oradata/orcl11g/redo01.log‘USER (ospid: 76747): terminating the instance due to error 313?因为日志文件丢失，启动三次失败后终止实例。可见，删除在线日志后数据库可以正常关闭，但却不能正常启动，下面进行恢复[oracle@cym1 trace]$ rman target /?Recovery Manager: Release 11.2.0.4.0 - Production on Mon Feb 26 04:57:55 2018Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.connected to target database: ORCL11G (DBID=1057360211, not open)?RMAN> alter database open resetlogs;?using target database control file instead of recovery catalogRMAN-00571: ===========================================================RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============RMAN-00571: ===========================================================RMAN-03002: failure of alter db command at 02/26/2018 04:58:18ORA-01139: RESETLOGS option only valid after an incomplete database recovery?RMAN> recover database;?Starting recover at 2018-02-26 04:58:48using channel ORA_DISK_1starting media recoverymedia recovery complete, elapsed time: 00:00:00Finished recover at 2018-02-26 04:58:49?RMAN> alter database open resetlogs;?database opened?RMAN> quit?Recovery Manager complete.?[oracle@cym1 trace]$ sqlplus / as sysdba?SQL*Plus: Release 11.2.0.4.0 Production on Mon Feb 26 04:59:00 2018Copyright (c) 1982, 2013, Oracle. All rights reserved.?Connected to:Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit ProductionWith the Partitioning, OLAP, Data Mining and Real Application Testing options?SQL> select * from v$log;? GROUP# THREAD# SEQUENCE# BYTES BLOCKSIZE MEMBERS ARC STATUS ---------- ---------- ---------- ---------- ---------- ---------- --- ---------------- 1 1 1 52428800 512 1 NO CURRENT 2 1 0 52428800 512 1 YES UNUSED 3 1 0 52428800 512 1 YES UNUSED ?SQL> select * from v$logfile;? GROUP# STATUS TYPE MEMBER IS_---------- ------- ------- -------------------------------------------------- --- 2 ONLINE /u01/app/oracle/oradata/orcl11g/redo02.log NO 3 ONLINE /u01/app/oracle/oradata/orcl11g/redo03.log NO 1 ONLINE /u01/app/oracle/oradata/orcl11g/redo01.log NO?SQL> quitDisconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit ProductionWith the Partitioning, OLAP, Data Mining and Real Application Testing options[oracle@cym1 trace]$ ll /u01/app/oracle/oradata/orcl11g/redo*-rw-r----- 1 oracle oinstall 52429312 Feb 26 04:59 /u01/app/oracle/oradata/orcl11g/redo01.log-rw-r----- 1 oracle oinstall 52429312 Feb 26 04:59 /u01/app/oracle/oradata/orcl11g/redo02.log-rw-r----- 1 oracle oinstall 52429312 Feb 26 04:59 /u01/app/oracle/oradata/orcl11g/redo03.log通过RestLogs 方式打开数据库后，恢复完成，在线日志文件已自行创建。任何数据的变更数据库都会先记录redo,才能写到数据文件。但是redo 日志都丢了，怎么数据库还能正常操作呢？不应该直接宕机吗？推测是因为Linux删除文件的机制导致，删除一个正在被使用的文件，Linux并没有真正删除它，关掉使用它的进程后，才会真正删除。下面验证：删除在线日志[oracle@cym1 ~]$ rm -rf /u01/app/oracle/oradata/orcl11g/redo0*[oracle@cym1 ~]$ ll /u01/app/oracle/oradata/orcl11g/redo*ls: cannot access /u01/app/oracle/oradata/orcl11g/redo*: No such file or directory[oracle@cym1 ~]$ sqlplus / as sysdba?SQL*Plus: Release 11.2.0.4.0 Production on Mon Feb 26 05:27:15 2018Copyright (c) 1982, 2013, Oracle. All rights reserved.?Connected to:Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit ProductionWith the Partitioning, OLAP, Data Mining and Real Application Testing options?SQL> select group#,thread#,sequence#,status from v$log;? GROUP# THREAD# SEQUENCE# STATUS---------- ---------- ---------- ---------------- 1 1 1 ACTIVE 2 1 2 ACTIVE 3 1 3 CURRENT?SQL> alter system switch logfile;?System altered......SQL> select group#,thread#,sequence#,status from v$log;? GROUP# THREAD# SEQUENCE# STATUS---------- ---------- ---------- ---------------- 1 1 7 ACTIVE 2 1 8 CURRENT 3 1 6 ACTIVE?SQL> 2. lsof 检查[oracle@cym1 ~]$ lsof -n | grep -i deletedoracle 76779 oracle 258u REG 253,0 52429312 800980 /u01/app/oracle/oradata/orcl11g/redo01.log (deleted)oracle 76779 oracle 259u REG 253,0 52429312 800981 /u01/app/oracle/oradata/orcl11g/redo02.log (deleted)oracle 76779 oracle 260u REG 253,0 52429312 800982 /u01/app/oracle/oradata/orcl11g/redo03.log (deleted)lsof 用来查看操作系统上被打开的文件，从以上来看在线日志文件仍然处于打开状态，说明还未被真正删除。进程ID为 76779，下面查看日志文件在操作系统上的真正位置：[oracle@cym1 ~]$ cd /proc/76779/fd[oracle@cym1 fd]$ ls0 1 10 11 12 13 14 2 256 257 258 259 260 261 262 263 264 265 266 267 268 3 4 5 6 7 8 9[oracle@cym1 fd]$ lltotal 0lr-x------ 1 oracle oinstall 64 Feb 26 05:29 0 -> /dev/nulll-wx------ 1 oracle oinstall 64 Feb 26 05:29 1 -> /dev/nulllrwx------ 1 oracle oinstall 64 Feb 26 05:29 10 -> /u01/app/oracle/product/11.2.0/dbhome_1/dbs/lkORCL11Glr-x------ 1 oracle oinstall 64 Feb 26 05:29 11 -> /u01/app/oracle/product/11.2.0/dbhome_1/rdbms/mesg/oraus.msbl-wx------ 1 oracle oinstall 64 Feb 26 05:29 12 -> /u01/app/oracle/diag/rdbms/orcl11g/orcl11g/trace/orcl11g_lgwr_76779.trcl-wx------ 1 oracle oinstall 64 Feb 26 05:29 13 -> /u01/app/oracle/diag/rdbms/orcl11g/orcl11g/trace/orcl11g_lgwr_76779.trmlrwx------ 1 oracle oinstall 64 Feb 26 05:29 14 -> socket:[748707]l-wx------ 1 oracle oinstall 64 Feb 26 05:29 2 -> /dev/nulllrwx------ 1 oracle oinstall 64 Feb 26 05:29 256 -> /u01/app/oracle/oradata/orcl11g/control01.ctllrwx------ 1 oracle oinstall 64 Feb 26 05:29 257 -> /u01/app/oracle/fast_recovery_area/orcl11g/control02.ctllrwx------ 1 oracle oinstall 64 Feb 26 05:29 258 -> /u01/app/oracle/oradata/orcl11g/redo01.log (deleted)lrwx------ 1 oracle oinstall 64 Feb 26 05:29 259 -> /u01/app/oracle/oradata/orcl11g/redo02.log (deleted)lrwx------ 1 oracle oinstall 64 Feb 26 05:29 260 -> /u01/app/oracle/oradata/orcl11g/redo03.log (deleted)lrwx------ 1 oracle oinstall 64 Feb 26 05:29 261 -> /u01/app/oracle/oradata/orcl11g/system01.dbflrwx------ 1 oracle oinstall 64 Feb 26 05:29 262 -> /u01/app/oracle/oradata/orcl11g/sysaux01.dbflrwx------ 1 oracle oinstall 64 Feb 26 05:29 263 -> /u01/app/oracle/oradata/orcl11g/undotbs01.dbflrwx------ 1 oracle oinstall 64 Feb 26 05:29 264 -> /u01/app/oracle/oradata/orcl11g/users01.dbflrwx------ 1 oracle oinstall 64 Feb 26 05:29 265 -> /u01/app/oracle/oradata/orcl11g/mgmt_depot.dbflrwx------ 1 oracle oinstall 64 Feb 26 05:29 266 -> /u01/app/oracle/oradata/orcl11g/mgmt.dbflrwx------ 1 oracle oinstall 64 Feb 26 05:29 267 -> /u01/app/oracle/oradata/orcl11g/mgmt_ad4j.dbflrwx------ 1 oracle oinstall 64 Feb 26 05:29 268 -> /u01/app/oracle/oradata/orcl11g/temp01.dbflr-x------ 1 oracle oinstall 64 Feb 26 05:29 3 -> /dev/nulllr-x------ 1 oracle oinstall 64 Feb 26 05:29 4 -> /dev/nulllr-x------ 1 oracle oinstall 64 Feb 26 05:29 5 -> /dev/nulllr-x------ 1 oracle oinstall 64 Feb 26 05:29 6 -> /u01/app/oracle/product/11.2.0/dbhome_1/rdbms/mesg/oraus.msblr-x------ 1 oracle oinstall 64 Feb 26 05:29 7 -> /proc/76779/fdlr-x------ 1 oracle oinstall 64 Feb 26 05:29 8 -> /dev/zerolrwx------ 1 oracle oinstall 64 Feb 26 05:29 9 -> /u01/app/oracle/product/11.2.0/dbhome_1/dbs/hc_orcl11g.dat可见在线日志对应的文件258/259/260还在，而且在数据库关闭前这3个资源是不会被释放的。这就解释了为什么删除在线日志文件不影响数据库正常操作。lrwx------ 1 oracle oinstall 64 Feb 26 05:29 258 -> /u01/app/oracle/oradata/orcl11g/redo01.log (deleted)lrwx------ 1 oracle oinstall 64 Feb 26 05:29 259 -> /u01/app/oracle/oradata/orcl11g/redo02.log (deleted)lrwx------ 1 oracle oinstall 64 Feb 26 05:29 260 -> /u01/app/oracle/oradata/orcl11g/redo03.log (deleted)下面关闭数据库，看看文件是不是被删除了SQL> shutdown immediate;Database closed.Database dismounted.ORACLE instance shut down.SQL> quitDisconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit ProductionWith the Partitioning, OLAP, Data Mining and Real Application Testing options[oracle@cym1 fd]$ ls[oracle@cym1 fd]$ lltotal 0[oracle@cym1 fd]$ cd ..-bash: cd: ..: No such file or directory[oracle@cym1 fd]$ ps -ef | grep 76779oracle 77010 76395 0 05:39 pts/0 00:00:00 grep 76779[oracle@cym1 fd]$ lsof -n | grep -i deleted随着数据库实例的关闭，Oracle 进程76779消失，所有被Oracle占用的资源全部释放。导致Online Redolog彻底被删除，数据库也就不能启动了。
