redo日誌檔案學習（22天)
阿新 • • 發佈：2022-05-04
關於redo日誌檔案，今天因為要做redo日誌的線上遷移，所以特意做了個簡單的總結。
1. 如果要把redo的切換資訊顯示到alert日誌中，需要設定個引數。
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> show parameter check
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_block_checking string FALSE
db_block_checksum string TYPICAL
log_checkpoint_interval integer 0
log_checkpoint_timeout integer 1800
log_checkpoints_to_alert boolean FALSE
SQL> alter system set log_checkpoints_to_alert=true;
System altered.
SQL> select group#,status from v$log;
GROUP# STATUS
---------- ----------------
1 INACTIVE
2 INACTIVE
3 INACTIVE
4 CURRENT
3.強制切換日誌，使用switch logfile,切換後，current日誌組切換到了第一組，剛剛的日誌組4變成了active狀態。 表示dbwr還沒有把髒資料寫入資料檔案。
需要出發dbwr來寫入，或者等待一會兒。 -alter system switch logfile;
Mon Mar 24 18:16:46 2014
Beginning log switch checkpoint up to RBA [0xb1d.2.10], SCN: 10583135604156
Thread 1 advanced to log sequence 2845 (LGWR switch)
Current log# 1 seq# 2845 mem# 0: /dbccbsPT1/oracle/PETCUS1/oracnt01/redolog_A1/redo/redo01A.log
Current log# 1 seq# 2845 mem# 1: /dbccbsPT1/oracle/PETCUS1/oracnt02/redolog_B1/redo/redo01B.log
Mon Mar 24 18:16:46 2014
Archived Log entry 2844 added for thread 1 sequence 2844 ID 0x4a0d6000 dest 1:
SQL> select group#,status from v$log;
GROUP# STATUS
---------- ----------------
1 CURRENT
2 INACTIVE
3 INACTIVE
4 ACTIVE--alter system switch logfile;
Mon Mar 24 18:17:35 2014
Beginning log switch checkpoint up to RBA [0xb1e.2.10], SCN: 10583135604180
Thread 1 advanced to log sequence 2846 (LGWR switch)
Current log# 3 seq# 2846 mem# 0: /dbccbsPT1/oracle/PETCUS1/oracnt01/redolog_A3/redo/redo03A.log
Current log# 3 seq# 2846 mem# 1: /dbccbsPT1/oracle/PETCUS1/oracnt02/redolog_B3/redo/redo03B.log
Mon Mar 24 18:17:35 2014
Archived Log entry 2845 added for thread 1 sequence 2845 ID 0x4a0d6000 dest 1:
SQL> select group#,status from v$log;
GROUP# STATUS
---------- ----------------
1 ACTIVE
2 INACTIVE
3 CURRENT
4 ACTIVE
5.如果進行全量檢查點，強制dbwr寫入資料檔案，可以出發全量檢查點。
alert日誌內容如下：
--alter system checkpoint;
Mon Mar 24 18:18:48 2014
Beginning global checkpoint up to RBA [0xb1e.4c.10], SCN: 10583135604229
Completed checkpoint up to RBA [0xb1e.4c.10], SCN: 10583135604229
Completed checkpoint up to RBA [0xb1e.2.10], SCN: 10583135604180
Completed checkpoint up to RBA [0xb1d.2.10], SCN: 10583135604156
SQL> select group#,status from v$log;
GROUP# STATUS
---------- ----------------
1 INACTIVE
2 INACTIVE
3 CURRENT
4 INACTIVE
6.過了一會兒，可以看到日誌中會出現增量檢查點，增量檢查點的優先順序比全量的要低。
Mon Mar 24 18:19:22 2014
Incremental checkpoint up to RBA [0xb1e.4c.0], current log tail at RBA [0xb1e.5f.0]
7.觸發日誌歸檔
--alter system archive log current;
Mon Mar 24 18:20:51 2014
ALTER SYSTEM ARCHIVE LOG
Mon Mar 24 18:20:51 2014
Beginning log switch checkpoint up to RBA [0xb1f.2.10], SCN: 10583135604443
Thread 1 advanced to log sequence 2847 (LGWR switch)
Current log# 2 seq# 2847 mem# 0: /dbccbsPT1/oracle/PETCUS1/oracnt01/redolog_A2/redo/redo02A.log
Current log# 2 seq# 2847 mem# 1: /dbccbsPT1/oracle/PETCUS1/oracnt02/redolog_B2/redo/redo02B.log
Archived Log entry 2846 added for thread 1 sequence 2846 ID 0x4a0d6000 dest 1:
SQL> select group#,status from v$log;
GROUP# STATUS
---------- ----------------
1 INACTIVE
2 CURRENT
3 ACTIVE
4 INACTIVE