Oracle Study之案例--Oracle 11g DataGuard Snapshot Standby
Oracle 11g的Data Guard不仅仅带给我们的是Active Data Guard实时查询特性,同时还带来了另外一个新特性，这便是Snapshot Standby数据库功能，此项功能可将备库置身于“可读写状态”用于不方便在生产环境主库中测试的内容，比如模拟上线测试等任务。当备库读写状态下任务完成后，可以非常轻松的完成Snapshot Standby数据库角色切换回备库角色，恢复与主库数据同步。在Snapshot Standby数据库状态下，备库是可以接收主库传过来的日志，但是不能对日志进行应用。
案例分析：
1、查看数据库信息
Primay DB: 14:47:09 SYS@ prod >select name,database_role,protection_mode from v$database; NAME DATABASE_ROLE PROTECTION_MODE --------- ---------------- -------------------- PROD PRIMARY MAXIMUM PERFORMANCE 14:46:52 SYS@ prod >select max(sequence#) from v$archived_log; MAX(SEQUENCE#) -------------- 536 Standby DB: 14:47:04 SYS@ shdb >select name,database_role,protection_mode from v$database; NAME DATABASE_ROLE PROTECTION_MODE --------- ---------------- -------------------- PROD PHYSICAL STANDBY MAXIMUM PERFORMANCE 14:46:09 SYS@ shdb >select max(sequence#) from v$archived_log; MAX(SEQUENCE#) -------------- 536
2、切换备库到Snapshot Standby
1）必须终止Media Recover Process 14:48:05 SYS@ shdb >alter database convert to snapshot standby; alter database convert to snapshot standby * ERROR at line 1: ORA-38784: Cannot create restore point 'SNAPSHOT_STANDBY_REQUIRED_11/27/2014 14:50:05'. ORA-01153: an incompatible media recovery is active 14:50:05 SYS@ shdb >recover managed standby database cancel; Media recovery complete. 2）必须建立Recover Area snapshot standby实际上是基于flashback database的运行机制，恢复到原先的standby状态 14:50:44 SYS@ shdb >alter database convert to snapshot standby; alter database convert to snapshot standby * ERROR at line 1: ORA-38784: Cannot create restore point 'SNAPSHOT_STANDBY_REQUIRED_11/27/2014 14:50:58'. ORA-38786: Recovery area is not enabled. 3）启用recover area 14:50:58 SYS@ shdb >show parameter recover NAME TYPE VALUE ------------------------------------ -------------------------------- ------------------------------ db_recovery_file_dest string db_recovery_file_dest_size big integer 0 recovery_parallelism integer 0 14:52:51 SYS@ shdb >alter system set db_recovery_file_dest_size=2g; System altered. 14:53:12 SYS@ shdb >alter system set db_recovery_file_dest='/dsk4/backup'; System altered. 14:53:18 SYS@ shdb >show parameter recover NAME TYPE VALUE ------------------------------------ -------------------------------- ------------------------------ db_recovery_file_dest string /dsk4/backup db_recovery_file_dest_size big integer 2G recovery_parallelism integer 3）转换成功 14:54:13 SYS@ shdb >alter database convert to snapshot standby; Database altered. Elapsed: 00:00:03.10 14:54:41 SYS@ shdb >select status from v$instance; STATUS ------------ MOUNTED 告警日志： 主库： LNS: Attempting destination LOG_ARCHIVE_DEST_2 network reconnect (3135) LNS: Destination LOG_ARCHIVE_DEST_2 network reconnect abandoned Errors in file /u01/app/oracle/diag/rdbms/bjdb/prod/trace/prod_nsa2_2960.trc: ORA-03135: connection lost contact Error 3135 for archive log file 5 to 'shdb' Errors in file /u01/app/oracle/diag/rdbms/bjdb/prod/trace/prod_nsa2_2960.trc: ORA-03135: connection lost contact LNS: Failed to archive log 5 thread 1 sequence 537 (3135) Errors in file /u01/app/oracle/diag/rdbms/bjdb/prod/trace/prod_nsa2_2960.trc: ORA-03135: connection lost contact 备库： alter database convert to snapshot standby ORA-38784 signalled during: alter database convert to snapshot standby... Thu Nov 27 14:53:12 2014 ALTER SYSTEM SET db_recovery_file_dest_size='2G' SCOPE=MEMORY; Using STANDBY_ARCHIVE_DEST parameter default value as USE_DB_RECOVERY_FILE_DEST ********************************************************** WARNING: Files may exists in db_recovery_file_dest that are not known to the database. Use the RMAN command CATALOG RECOVERY AREA to re-catalog any such files. If files cannot be cataloged, then manually delete them using OS command. One of the following events caused this: 1. A backup controlfile was restored. 2. A standby controlfile was restored. 3. The controlfile was re-created. 4. db_recovery_file_dest had previously been enabled and then disabled. ********************************************************** ALTER SYSTEM SET db_recovery_file_dest='/dsk4/backup' SCOPE=MEMORY; Thu Nov 27 14:53:18 2014 db_recovery_file_dest_size of 2048 MB is 0.00% used. This is a user-specified limit on the amount of space that will be used by this database for recovery-related files, and does not reflect the amount of space available in the underlying filesystem or ASM diskgroup. Thu Nov 27 14:54:38 2014 alter database convert to snapshot standby Starting background process RVWR Thu Nov 27 14:54:38 2014 RVWR started with pid=21, OS id=2198 Allocated 3981204 bytes in shared pool for flashback generation buffer Created guaranteed restore point SNAPSHOT_STANDBY_REQUIRED_11/27/2014 14:54:38 krsv_proc_kill: Killing 3 processes (all RFS) CLOSE: killing server sessions. CLOSE: all sessions shutdown successfully. Thu Nov 27 14:54:41 2014 SMON: disabling cache recovery Begin: Standby Redo Logfile archival End: Standby Redo Logfile archival RESETLOGS after incomplete recovery UNTIL CHANGE 8596005 Resetting resetlogs activation ID 219765236 (0xd1959f4) Online log /dsk2/oradata/shdb/redo04b.log: Thread 1 Group 4 was previously cleared Online log /dsk1/oradata/shdb/redo04a.log: Thread 1 Group 4 was previously cleared Online log /dsk2/oradata/shdb/redo05b.log: Thread 1 Group 5 was previously cleared Online log /dsk1/oradata/shdb/redo05a.log: Thread 1 Group 5 was previously cleared Standby became primary SCN: 8596003 Thu Nov 27 14:54:41 2014 Setting recovery target incarnation to 3 CONVERT TO SNAPSHOT STANDBY: Complete - Database mounted as snapshot standby Completed: alter database convert to snapshot standby 14:54:55 SYS@ shdb >select database_role,open_mode from v$database; DATABASE_ROLE OPEN_MODE ---------------- -------------------- SNAPSHOT STANDBY MOUNTED
Created guaranteed restore point SNAPSHOT_STANDBY_REQUIRED_11/27/2014 14:54:38 在日志中可以看到，Database建立了restore point
3、Open Database验证
1）open database 14:57:02 SYS@ shdb >alter database open; Database altered. 14:57:33 SYS@ shdb >select database_role,open_mode from v$database; DATABASE_ROLE OPEN_MODE ---------------- -------------------- SNAPSHOT STANDBY READ WRITE 2）日志切换： 主库： 14:47:31 SYS@ prod >alter system switch logfile; System altered. 15:01:11 SYS@ prod >/ System altered. 15:01:23 SYS@ prod >select max(sequence#) from v$archived_log; MAX(SEQUENCE#) -------------- 539 告警日志： Thread 1 advanced to log sequence 538 (LGWR switch) Current log# 4 seq# 538 mem# 0: /dsk2/oradata/prod/redo04b.log Current log# 4 seq# 538 mem# 1: /dsk1/oradata/prod/redo04a.log Thu Nov 27 14:59:46 2014 Archived Log entry 504 added for thread 1 sequence 537 ID 0xd1959f4 dest 1: Thu Nov 27 15:00:53 2014 Thread 1 cannot allocate new log, sequence 539 Checkpoint not complete Current log# 4 seq# 538 mem# 0: /dsk2/oradata/prod/redo04b.log Current log# 4 seq# 538 mem# 1: /dsk1/oradata/prod/redo04a.log Thu Nov 27 15:01:11 2014 Thread 1 advanced to log sequence 539 (LGWR switch) Current log# 5 seq# 539 mem# 0: /dsk2/oradata/prod/redo05b.log Current log# 5 seq# 539 mem# 1: /dsk1/oradata/prod/redo05a.log Thu Nov 27 15:01:12 2014 Archived Log entry 507 added for thread 1 sequence 538 ID 0xd1959f4 dest 1: Thread 1 cannot allocate new log, sequence 540 Checkpoint not complete Current log# 5 seq# 539 mem# 0: /dsk2/oradata/prod/redo05b.log Current log# 5 seq# 539 mem# 1: /dsk1/oradata/prod/redo05a.log Thu Nov 27 15:01:23 2014 Thread 1 advanced to log sequence 540 (LGWR switch) Current log# 4 seq# 540 mem# 0: /dsk2/oradata/prod/redo04b.log Current log# 4 seq# 540 mem# 1: /dsk1/oradata/prod/redo04a.log Thu Nov 27 15:01:25 2014 Archived Log entry 509 added for thread 1 sequence 539 ID 0xd1959f4 dest 1: 备库： 14:57:49 SYS@ shdb >select max(sequence#) from v$archived_log; MAX(SEQUENCE#) -------------- 539 告警日志： RFS[6]: Assigned to RFS process 2254 RFS[6]: Identified database type as 'snapshot standby': Client is ARCH pid 2953 Thu Nov 27 14:59:45 2014 RFS[7]: Assigned to RFS process 2256 RFS[7]: Identified database type as 'snapshot standby': Client is LGWR ASYNC pid 2960 RFS[7]: Opened log for thread 1 sequence 537 dbid 219724276 branch 807885951 Archived Log entry 24 added for thread 1 sequence 537 rlc 807885951 ID 0xd1959f4 dest 2: RFS[7]: Opened log for thread 1 sequence 538 dbid 219724276 branch 807885951 Thu Nov 27 15:01:12 2014 Archived Log entry 25 added for thread 1 sequence 538 rlc 807885951 ID 0xd1959f4 dest 2: RFS[7]: Opened log for thread 1 sequence 539 dbid 219724276 branch 807885951 Thu Nov 27 15:01:23 2014 Archived Log entry 26 added for thread 1 sequence 539 rlc 807885951 ID 0xd1959f4 dest 2: RFS[7]: Opened log for thread 1 sequence 540 dbid 219724276 branch 807885951 -----可以看到备库只是接收日志，并不对日志进行apply。 3）在备库做DML和压力测试: 15:03:52 SCOTT@ shdb >begin 15:03:59 2 for i in 1..10000 loop 15:04:06 3 insert into t2 values (i,i*10); 15:04:29 4 end loop; 15:04:34 5 commit; 15:04:35 6 end; 15:04:37 7 / PL/SQL procedure successfully completed. Elapsed: 00:00:04.43 15:04:42 SCOTT@ shdb >select count(*) from t2; COUNT(*) ---------- 10003
4、将数据库切回Physical Standby
1） 关闭数据库，启动到mount 15:06:10 SYS@ shdb >shutdown immediate; Database closed. Database dismounted. ORACLE instance shut down. 15:06:25 SYS@ shdb >startup mount; ORACLE instance started. Total System Global Area 330600448 bytes Fixed Size 1336344 bytes Variable Size 113249256 bytes Database Buffers 209715200 bytes Redo Buffers 6299648 bytes Database mounted. 2）转换到Physical Standby 15:06:57 SYS@ shdb >alter database convert to physical standby; Database altered. 备库告警日志： Using STANDBY_ARCHIVE_DEST parameter default value as /dsk4/arch_shdb RFS[1]: Assigned to RFS process 2423 RFS[1]: Identified database type as 'snapshot standby': Client is ARCH pid 2953 Thu Nov 27 15:06:44 2014 RFS[2]: Assigned to RFS process 2425 RFS[2]: Identified database type as 'snapshot standby': Client is LGWR ASYNC pid 2960 RFS[2]: Opened log for thread 1 sequence 540 dbid 219724276 branch 807885951 Archived Log entry 28 added for thread 1 sequence 540 rlc 807885951 ID 0xd1959f4 dest 2: RFS[2]: Opened log for thread 1 sequence 541 dbid 219724276 branch 807885951 Thu Nov 27 15:06:53 2014 RFS[3]: Assigned to RFS process 2427 RFS[3]: Identified database type as 'snapshot standby': Client is ARCH pid 2953 Thu Nov 27 15:07:09 2014 alter database convert to physical standby ALTER DATABASE CONVERT TO PHYSICAL STANDBY (shdb) krsv_proc_kill: Killing 2 processes (all RFS) Flashback Restore Start Flashback Restore Complete Stopping background process RVWR Deleted Oracle managed file /dsk4/backup/SHDB/flashback/o1_mf_b7flogt9_.flb Guaranteed restore point dropped Clearing standby activation ID 276569850 (0x107c1efa) The primary database controlfile was created using the 'MAXLOGFILES 16' clause. There is space for up to 14 standby redo logfiles Use the following SQL commands on the standby database to create standby redo logfiles that match the primary database: ALTER DATABASE ADD STANDBY LOGFILE 'srl1.f' SIZE 4194304; ALTER DATABASE ADD STANDBY LOGFILE 'srl2.f' SIZE 4194304; ALTER DATABASE ADD STANDBY LOGFILE 'srl3.f' SIZE 4194304; Completed: alter database convert to physical standby 3）转换后，数据库处于非mount状态 15:07:10 SYS@ shdb >select database_role,open_mode from v$database; select database_role,open_mode from v$database * ERROR at line 1: ORA-01507: database not mounted 15:08:29 SYS@ shdb >alter database mount; alter database mount * ERROR at line 1: ORA-00750: database has been previously mounted and dismounted 15:08:39 SYS@ shdb >shutdown immediate; ORA-01507: database not mounted ORACLE instance shut down. 15:09:28 SYS@ shdb >startup ORACLE instance started. Total System Global Area 330600448 bytes Fixed Size 1336344 bytes Variable Size 113249256 bytes Database Buffers 209715200 bytes Redo Buffers 6299648 bytes Database mounted. Database opened. 4）转换成Physical Standby 15:09:39 SYS@ shdb >select database_role,open_mode from v$database; DATABASE_ROLE OPEN_MODE ---------------- -------------------- PHYSICAL STANDBY READ ONLY 备库告警日志： Physical standby database opened for read only access. Completed: ALTER DATABASE OPEN ARC2: Archival started ARC0: STARTING ARCH PROCESSES COMPLETE ARC0: Becoming the heartbeat ARCH Thu Nov 27 15:09:40 2014 Using STANDBY_ARCHIVE_DEST parameter default value as /dsk4/arch_shdb RFS[1]: Assigned to RFS process 2763 RFS[1]: Identified database type as 'physical standby': Client is ARCH pid 2953 Thu Nov 27 15:09:46 2014 RFS[2]: Assigned to RFS process 2765 RFS[2]: Identified database type as 'physical standby': Client is LGWR ASYNC pid 2960 Primary database is in MAXIMUM PERFORMANCE mode RFS[2]: Opened log for thread 1 sequence 541 dbid 219724276 branch 807885951 Archived Log entry 29 added for thread 1 sequence 541 rlc 807885951 ID 0xd1959f4 dest 2: RFS[2]: Opened log for thread 1 sequence 542 dbid 219724276 branch 807885951 Thu Nov 27 15:09:53 2014 RFS[3]: Assigned to RFS process 2768 RFS[3]: Identified database type as 'physical standby': Client is ARCH pid 2953 主库告警日志： Using STANDBY_ARCHIVE_DEST parameter default value as /dsk4/arch_prod ALTER SYSTEM SET log_archive_dest_state_2='ENABLE' SCOPE=MEMORY SID='*'; Thu Nov 27 15:09:42 2014 Thread 1 cannot allocate new log, sequence 542 Checkpoint not complete Current log# 5 seq# 541 mem# 0: /dsk2/oradata/prod/redo05b.log Current log# 5 seq# 541 mem# 1: /dsk1/oradata/prod/redo05a.log Thu Nov 27 15:09:46 2014 ****************************************************************** LGWR: Setting 'active' archival for destination LOG_ARCHIVE_DEST_2 ****************************************************************** Thread 1 advanced to log sequence 542 (LGWR switch) Current log# 4 seq# 542 mem# 0: /dsk2/oradata/prod/redo04b.log Current log# 4 seq# 542 mem# 1: /dsk1/oradata/prod/redo04a.log Thu Nov 27 15:09:48 2014 Archived Log entry 513 added for thread 1 sequence 541 ID 0xd1959f4 dest 1 5）查看Snapshot状态下创建的数据已经被还原 15:09:50 SYS@ shdb >conn scott/tiger Connected. 15:12:49 SCOTT@ shdb >select count(*) from t2; COUNT(*) ---------- 3
小结
Oracle 11g DataGuar增加的Snapshot Standby数据库”功能，备库可以临时成为一个可读写的独立数据库，这极大的扩展了备库的应用场合，我们可以使用备库的这一项特殊功能将那些在生产环境中“不敢”模拟和再现的问题在备库端进行测试，测试完毕后再恢复其物理备库的身份进行日志恢复，极大的方便我们在日常生产环境中对DG的应用。