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如何進行oracle switch logfile日志切換以及alter system checkpoint做了什么

發(fā)布時間：2021-11-09 11:05:46 來源：億速云閱讀：310 作者：柒染欄目：建站服務器

本篇文章為大家展示了如何進行oracle switch logfile日志切換以及alter system checkpoint做了什么，內容簡明扼要并且容易理解，絕對能使你眼前一亮，通過這篇文章的詳細介紹希望你能有所收獲。

日志切換或checkpoint到底發(fā)生了什么？
　　　1,剛變成active的日志文件（即由last_change#到next_change#的redo）被　dbwr寫入到數(shù)據(jù)文件

　　　2,ckpt更新所有數(shù)據(jù)文件頭的start scn即v$datafile_header.checkpoint_change#為剛變成active的日志文件
　　　　的first_change#

　　　3,ckpt同時更新控制文件的檢查點scn,即v$database.checkpoint_change#為active狀態(tài)日志文件的first_change#

/***********測試開始*************/
/**********檢查點發(fā)生前的數(shù)據(jù)文件頭scn*********/
SQL> select checkpoint_change# from v$datafile_header;

CHECKPOINT_CHANGE#
------------------
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730

CHECKPOINT_CHANGE#
------------------
          10590730

21 rows selected

SQL> select * from v$log;

    GROUP#    THREAD# SEQUENCE#      BYTES BLOCKSIZE    MEMBERS ARCHIVED STATUS           FIRST_CHANGE# FIRST_TIME NEXT_CHANGE# NEXT_TIME
---------- ---------- ---------- ---------- ---------- ---------- -------- ---------------- ------------- ----------- ------------ -----------
         3          1        817   52428800        512          1 NO       INACTIVE              10453013 2013/3/24 1     10454569 2013/3/24 1
         4          1        818 209715200        512          1 NO       INACTIVE              10454569 2013/3/24 1     10492795 2013/3/24 1
         5          1        819 209715200        512          1 NO       INACTIVE              10492795 2013/3/24 1     10560992 2013/3/25 1
         6          1        820 209715200        512          1 NO       INACTIVE              10560992 2013/3/25 1     10561002 2013/3/25 1
         7          1        821 209715200        512          1 NO       INACTIVE              10561002 2013/3/25 1     10561202 2013/3/25 1
         8          1        822 209715200        512          1 NO       INACTIVE              10561202 2013/3/25 1     10588922 2013/3/25 1
         9          1        816 209715200        512          1 NO       INACTIVE              10446578 2013/3/24 1     10453013 2013/3/24 1
        10          1        823   20971520        512          1 NO       CURRENT               10588922 2013/3/25 1 281474976710

8 rows selected

SQL> select checkpoint_change# from v$database;

CHECKPOINT_CHANGE#
------------------
          10590730

SQL> select checkpoint_change# from v$datafile;

CHECKPOINT_CHANGE#
------------------
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730

CHECKPOINT_CHANGE#
------------------
          10590730

21 rows selected

/*********日志切換后各個scn*****************/
SQL> alter system switch logfile;

System altered

SQL> select checkpoint_change# from v$datafile;

CHECKPOINT_CHANGE#
------------------
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730

CHECKPOINT_CHANGE#
------------------
          10590730

21 rows selected

SQL> select checkpoint_change# from v$database;

CHECKPOINT_CHANGE#
------------------
10590730

SQL> select * from v$log;

    GROUP#    THREAD# SEQUENCE#      BYTES BLOCKSIZE    MEMBERS ARCHIVED STATUS           FIRST_CHANGE# FIRST_TIME NEXT_CHANGE# NEXT_TIME
---------- ---------- ---------- ---------- ---------- ---------- -------- ---------------- ------------- ----------- ------------ -----------
         3          1        817   52428800        512          1 NO       INACTIVE              10453013 2013/3/24 1     10454569 2013/3/24 1
         4          1        818 209715200        512          1 NO       INACTIVE              10454569 2013/3/24 1     10492795 2013/3/24 1
         5          1        819 209715200        512          1 NO       INACTIVE              10492795 2013/3/24 1     10560992 2013/3/25 1
         6          1        820 209715200        512          1 NO       INACTIVE              10560992 2013/3/25 1     10561002 2013/3/25 1
         7          1        821 209715200        512          1 NO       INACTIVE              10561002 2013/3/25 1     10561202 2013/3/25 1
         8          1        822 209715200        512          1 NO       INACTIVE              10561202 2013/3/25 1     10588922 2013/3/25 1
         9          1        824 209715200        512          1 NO       CURRENT               10591778 2013/3/25 1 281474976710
        10          1        823   20971520        512          1 NO       ACTIVE                10588922 2013/3/25 1     10591778 2013/3/25 1

8 rows selected

SQL> select checkpoint_change# from v$datafile_header;

CHECKPOINT_CHANGE#
------------------
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730

CHECKPOINT_CHANGE#
------------------
          10590730

21 rows selected

小結：alter system checkpoint不會觸發(fā)變更數(shù)據(jù)文件及數(shù)據(jù)文件頭的檢查點scn

/***********再看下日志切換是怎么樣的情況********************/
/**************日志切換前*************************/
SQL> select checkpoint_change# from v$datafile_header;

CHECKPOINT_CHANGE#
------------------
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730

CHECKPOINT_CHANGE#
------------------
          10590730

21 rows selected

SQL> select checkpoint_change# from v$datafile;

CHECKPOINT_CHANGE#
------------------
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730
          10590730

CHECKPOINT_CHANGE#
------------------
          10590730

21 rows selected

SQL> select checkpoint_change# from v$database;

CHECKPOINT_CHANGE#
------------------
          10590730

SQL> select * from v$log;

    GROUP#    THREAD# SEQUENCE#      BYTES BLOCKSIZE    MEMBERS ARCHIVED STATUS           FIRST_CHANGE# FIRST_TIME NEXT_CHANGE# NEXT_TIME
---------- ---------- ---------- ---------- ---------- ---------- -------- ---------------- ------------- ----------- ------------ -----------
         3          1        817   52428800        512          1 NO       INACTIVE              10453013 2013/3/24 1     10454569 2013/3/24 1
         4          1        818 209715200        512          1 NO       INACTIVE              10454569 2013/3/24 1     10492795 2013/3/24 1
         5          1        819 209715200        512          1 NO       INACTIVE              10492795 2013/3/24 1     10560992 2013/3/25 1
         6          1        820 209715200        512          1 NO       INACTIVE              10560992 2013/3/25 1     10561002 2013/3/25 1
         7          1        821 209715200        512          1 NO       INACTIVE              10561002 2013/3/25 1     10561202 2013/3/25 1
         8          1        822 209715200        512          1 NO       INACTIVE              10561202 2013/3/25 1     10588922 2013/3/25 1
         9          1        824 209715200        512          1 NO       CURRENT               10591778 2013/3/25 1 281474976710
        10          1        823   20971520        512          1 NO       ACTIVE                10588922 2013/3/25 1     10591778 2013/3/25 1

8 rows selected

SQL>

/***********日志切換后****************/
SQL> alter system switch logfile;

System altered

SQL> select * from v$log;

    GROUP#    THREAD# SEQUENCE#      BYTES BLOCKSIZE    MEMBERS ARCHIVED STATUS           FIRST_CHANGE# FIRST_TIME NEXT_CHANGE# NEXT_TIME
---------- ---------- ---------- ---------- ---------- ---------- -------- ---------------- ------------- ----------- ------------ -----------
         3          1        825   52428800        512          1 NO       CURRENT               10592541 2013/3/25 1 281474976710
         4          1        818 209715200        512          1 NO       INACTIVE              10454569 2013/3/24 1     10492795 2013/3/24 1
         5          1        819 209715200        512          1 NO       INACTIVE              10492795 2013/3/24 1     10560992 2013/3/25 1
         6          1        820 209715200        512          1 NO       INACTIVE              10560992 2013/3/25 1     10561002 2013/3/25 1
         7          1        821 209715200        512          1 NO       INACTIVE              10561002 2013/3/25 1     10561202 2013/3/25 1
         8          1        822 209715200        512          1 NO       INACTIVE              10561202 2013/3/25 1     10588922 2013/3/25 1
         9          1        824 209715200        512          1 NO       ACTIVE                10591778 2013/3/25 1     10592541 2013/3/25 1
        10          1        823   20971520        512          1 NO       INACTIVE              10588922 2013/3/25 1     10591778 2013/3/25 1

8 rows selected

/***參考上面日志信息，控制文件的檢查點scn及數(shù)據(jù)文件及數(shù)據(jù)文件頭的scn已經(jīng)更新active日志的first_change#/
SQL> select checkpoint_change# from v$database;

CHECKPOINT_CHANGE#
------------------
          10591778

SQL> select checkpoint_change# from v$datafile;

CHECKPOINT_CHANGE#
------------------
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778

CHECKPOINT_CHANGE#
------------------
          10591778

21 rows selected

SQL> select checkpoint_change# from v$datafile_header;

CHECKPOINT_CHANGE#
------------------
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778
          10591778

CHECKPOINT_CHANGE#
------------------
          10591778

21 rows selected

上述內容就是如何進行oracle switch logfile日志切換以及alter system checkpoint做了什么，你們學到知識或技能了嗎？如果還想學到更多技能或者豐富自己的知識儲備，歡迎關注億速云行業(yè)資訊頻道。

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