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丢失控制文件后，用脚本重建控制文件，打开数据库时可不必指定RESETLOGS选项，不会产生新的incarnation，但是会丢失原来控制文件中信息，如RMAN配置与备份记录、incarnation表。
Well last week I had a few posts about controlfile recovery; one about recovering without a backup and one about recovering with a backup using RESETLOGS. In the second post I showed how when you restore a backup controlfile Oracle will always require you to recover then open the database with RESETLOGS.
Hemant Chitale pointed out that you do not always need to do a RESETLOGS when you open the database. If you recreate the controlfile rather than restoring a backup then Oracle allows you to open the database normally (assuming of course a normal database shutdown). Naturally you will lose any information in your controlfile (RMAN configuration and records, the incarnation table, etc) so I would personally prefer keeping the old file. But it’s certainly possible – so here’s a demo of Hemant’s suggestion on Oracle 10 release 2. Really it’s abit of a rehash; Hemant actually posted all of this himself on oracle-l last week. (And more – he also posted a scenario of losing both the controlfile and online logs.) He also mentioned it in his blog. So for more detail you can also check out email.
The setup is exactly the same as recovery with a backup controlfile – I’m just going to do some different steps starting at the “Recovery” part:
Recovery
We’ll pick up from the other post with the attempt to open the database that fails. Remember that I have already restored a backup controlfile and mounted it.
SQL> alter database open noresetlogs;
alter database open noresetlogs
*
ERROR at line 1:
ORA-01588: must use RESETLOGS option for database openNow if you already have a backup of your controlfile then you’re all set. But of course if you don’t you can even make one using your controlfile backup. That’s what I did here:
SQL> alter database backup controlfile to trace2 as '/u04/oracle/oradata/jt10g/newctl.sql';Database altered.Now one thing that we’re definitely going to lose is the incarnation table. Let’s have a quick look at the contents right now.
SQL> select * from v$database_incarnation;INCARNATION# RESETLOGS_CHANGE# RESETLOGS PRIOR_RESETLOGS_CHANGE# PRIOR_RES
------------ ----------------- --------- ----------------------- ---------
STATUS RESETLOGS_ID PRIOR_INCARNATION# FLASHBACK_DATABASE_ALLOWED
------- ------------ ------------------ --------------------------1 1 12-JUL-05 0
PARENT 563434975 0 NO2 524107 03-MAY-07 1 12-JUL-05
PARENT 621607779 1 NO3 565455 03-MAY-07 524107 03-MAY-07
PARENT 621627183 2 NO4 784376 09-MAY-07 565455 03-MAY-07
CURRENT 622130726 3 NORecreating the Control File
It’s worth quickly pointing out that you can of course do this as long as you can generate the proper CREATE CONTROLFILE statement. If you know your datafile and logfile layout then you can generate this statement even with no backup of anything. Of course the best way to get it is with “backup to trace”.
First you need to have the instance started but no controlfile mounted. When you recreate the controlfile it will read the CONTROL_FILES initialization parameter and overwrite any existing files.
SQL> shutdown immediate;
ORA-01109: database not openDatabase dismounted.
ORACLE instance shut down.SQL> startup nomount
ORACLE instance started.Total System Global Area 629145600 bytes
Fixed Size 1980712 bytes
Variable Size 180356824 bytes
Database Buffers 440401920 bytes
Redo Buffers 6406144 bytesSQL> CREATE CONTROLFILE REUSE DATABASE "JT10G" NORESETLOGS NOARCHIVELOG2 MAXLOGFILES 163 MAXLOGMEMBERS 34 MAXDATAFILES 1005 MAXINSTANCES 86 MAXLOGHISTORY 2927 LOGFILE8 GROUP 1 '/u04/oracle/oradata/jt10g/redo01.log' SIZE 50M,9 GROUP 2 '/u04/oracle/oradata/jt10g/redo02.log' SIZE 50M,10 GROUP 3 '/u04/oracle/oradata/jt10g/redo03.log' SIZE 50M11 DATAFILE12 '/u04/oracle/oradata/jt10g/system01.dbf',13 '/u04/oracle/oradata/jt10g/undotbs01.dbf',14 '/u04/oracle/oradata/jt10g/sysaux01.dbf',15 '/u04/oracle/oradata/jt10g/users01.dbf',16 '/u04/oracle/oradata/jt10g/example01.dbf'17 CHARACTER SET WE8ISO8859P118 ;Control file created.SQL> ALTER DATABASE OPEN;Database altered.I got that statement out of a trace file. Also you need to remember to recreate your tempfiles; the appropriate statements will also be in your trace file.
SQL> ALTER TABLESPACE TEMP2 ADD TEMPFILE '/u04/oracle/oradata/jt10g/temp01.dbf' REUSE;Tablespace altered.Now as I mentioned before you will lose all information in your controlfile. Let’s quickly verify this by examining the incarnation table.
SQL> select * from v$database_incarnation;INCARNATION# RESETLOGS_CHANGE# RESETLOGS PRIOR_RESETLOGS_CHANGE# PRIOR_RES
------------ ----------------- --------- ----------------------- ---------
STATUS RESETLOGS_ID PRIOR_INCARNATION# FLASHBACK_DATABASE_ALLOWED
------- ------------ ------------------ --------------------------1 784376 09-MAY-07 565455 03-MAY-07
CURRENT 622130726 0 NOAnd there you have it. Controlfile recovery without a RESETLOGS. As I mentioned before I prefer the RESETLOGS case and keeping the original controlfile if at all possible. Perhaps the main reason is that incarnations exist for a reason; they help you keep track of changes to you database. It’s good to have that electronic record. But this is also a very important recovery method to be aware of!
FROM: http://www.ardentperf.com/2007/05/15/controlfile-recovery-without-resetlogs/
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