什么意思呢?"/>
oracle的scn是什么,请问这个scn到底指什么意思呢?
我做了测试,好象commit并没有改变scn,大家慢慢看吧,这里面还透露些问题
SQL> select name,resetlogs_change#,checkpoint_change#,controlfile_change# from v$database;
NAME RESETLOGS_CHANGE# CHECKPOINT_CHANGE# CONTROLFILE_CHANGE#
--------- ----------------- ------------------ -------------------
CZNDB 190578 3598764 3598764
SQL> select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS
---------- ---------- ---------- ---------- ---------- --- ----------------
FIRST_CHANGE# FIRST_TIME
------------- ----------
1 1 164 104857600 1 NO CURRENT
3598763 24-1月 -07
2 1 162 104857600 1 NO INACTIVE
3531638 23-1月 -07
3 1 163 104857600 1 NO INACTIVE
3554885 23-1月 -07
SQL> alter system switch logfile;
系统已更改。
SQL> select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS
---------- ---------- ---------- ---------- ---------- --- ----------------
FIRST_CHANGE# FIRST_TIME
------------- ----------
1 1 164 104857600 1 NO ACTIVE
3598763 24-1月 -07
2 1 165 104857600 1 NO CURRENT
3633326 24-1月 -07
3 1 163 104857600 1 NO INACTIVE
3554885 23-1月 -07
SQL> select name,resetlogs_change#,checkpoint_change#,controlfile_change# from v$database;
NAME RESETLOGS_CHANGE# CHECKPOINT_CHANGE# CONTROLFILE_CHANGE#
--------- ----------------- ------------------ -------------------
CZNDB 190578 3598764 3633326
SQL> insert into scott.aa select * from scott.aa;
已创建32行。
SQL> select name,resetlogs_change#,checkpoint_change#,controlfile_change# from v$database;
NAME RESETLOGS_CHANGE# CHECKPOINT_CHANGE# CONTROLFILE_CHANGE#
--------- ----------------- ------------------ -------------------
CZNDB 190578 3598764 3633326
SQL> commit;
提交完成。
SQL> select name,resetlogs_change#,checkpoint_change#,controlfile_change# from v$database;
NAME RESETLOGS_CHANGE# CHECKPOINT_CHANGE# CONTROLFILE_CHANGE#
--------- ----------------- ------------------ -------------------
CZNDB 190578 3598764 3633326
SQL> alter system switch logfile;
系统已更改。
SQL> select name,resetlogs_change#,checkpoint_change#,controlfile_change# from v$database;
NAME RESETLOGS_CHANGE# CHECKPOINT_CHANGE# CONTROLFILE_CHANGE#
--------- ----------------- ------------------ -------------------
CZNDB 190578 3633326 3633675
SQL> select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS
---------- ---------- ---------- ---------- ---------- --- ----------------
FIRST_CHANGE# FIRST_TIME
------------- ----------
1 1 164 104857600 1 NO INACTIVE
3598763 24-1月 -07
2 1 165 104857600 1 NO ACTIVE
3633326 24-1月 -07
3 1 166 104857600 1 NO CURRENT
3633674 24-1月 -07
SQL> alter system checkpoint;
系统已更改。
SQL> select name,resetlogs_change#,checkpoint_change#,controlfile_change# from v$database;
NAME RESETLOGS_CHANGE# CHECKPOINT_CHANGE# CONTROLFILE_CHANGE#
--------- ----------------- ------------------ -------------------
CZNDB 190578 3633782 3633782
SQL> select * from v$log;
GROUP# THREAD# SEQUENCE# BYTES MEMBERS ARC STATUS
---------- ---------- ---------- ---------- ---------- --- ----------------
FIRST_CHANGE# FIRST_TIME
------------- ----------
1 1 164 104857600 1 NO INACTIVE
3598763 24-1月 -07
2 1 165 104857600 1 NO INACTIVE
3633326 24-1月 -07
3 1 166 104857600 1 NO CURRENT
3633674 24-1月 -07
SQL>
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oracle的scn是什么,请问这个scn到底指什么意思呢?
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