Re: recovery stops due to missing datafile

From: Hieraklion <hieraklion_at_spray.fr>
Date: Wed, 06 Jun 2001 14:03:44 +0200
Message-ID: <3B1E1C20.796C659B@spray.fr>

"Bonjour" from Paris,

You can try this :

Current controlfile, backup of datafile exists (Oracle release 7.x). I tested successfully on 8.0.5.

A valid (either hot or cold) backup of the datafiles exists, except for the datafile created since the backup was taken. The current controlfile exists. The database is in archivelog mode (see note (c) at bottom of page).

Restore ONLY the datafiles (those that have been lost or damaged) from the last hot or cold backup. The current online redo logs and control file(s) must be intact.
Mount the database
Create a new datafile using the 'ALTER DATABASE CREATE DATAFILE' command.
The datafile can be created with the same name as the original file. For example,

        SQLDBA> alter database create datafile
             2> '/dev1/oracle/dbs/testtbs.dbf';
        Statement processed.

     b. The datafile can be created with a different filename to the original.
        This option might be chosen if the original file was lost due to disk
        failure and the failed disk was still unavailable; the new file would
        then be created on a different device. For example,

        SQLDBA> alter database create datafile
             2> '/dev1/oracle/dbs/testtbs.dbf'
             3> as
             4> '/dev2/oracle/dbs/testtbs.dbf';
        Statement processed.

        The above command creates a new datafile on the dev2 device. The file
        is created using information, stored in the control file, from the
        original file. The command implicitly renames the filename in the
        control file.

        NOTE: IT IS VERY IMPORTANT TO SPECIFY THE CORRECT FILENAME WHEN
              RECREATING THE LOST DATAFILE. IF YOU SPECIFY AN EXISTING
              ORACLE DATAFILE, THAT DATAFILE WILL BE INITIALISED AND WILL
              ITSELF REQUIRE RECOVERY.

4. Recover the database.

     SQLDBA> recover database
     ORA-00279: Change 6677 generated at 06/03/97 15:20:24 needed for thread 1
     ORA-00289: Suggestion : /dev1/oracle/dbs/arch/arch000074.arc
     ORA-00280: Change 6677 for thread 1 is in sequence #74
     Specify log: {<RET>=suggested | filename | AUTO | CANCEL}

     At this point the recovery procedure will wait for the user to supply the
     information requested regarding the name and location of the archived log
     files. For example, entering AUTO directs Oracle to apply the suggested
     redo log and any others that it requires to recover the datafiles.

     Applying suggested logfile...
     Log applied.


               :

               :

     <Application of further redo logs>


               :

               :

     Media recovery complete.

5. Open the database

     SQLDBA> alter database open;
     Statement processed.

B. Old controlfile, no backup of datafile (Oracle release 7.3.x). I tested successfully on 8.0.5.

A valid (either hot or cold) backup of the datafiles exists, except for the datafile created since the backup was taken. The controlfile is a backup from before the creation of the new datafile. The database is in archivelog mode (see note (c) at bottom of page).

Restore the datafiles (those that have been lost or damaged) from the last hot or cold backup. Also restore the old copy of the controlfile. The current online redo logs must be intact.
Mount the database
Start media recovery, specifying backup controlfile

     SVRMGR> recover database using backup controlfile
     ORA-00279: Change 6677 generated at 06/03/97 15:20:24 needed for thread 1
     ORA-00289: Suggestion : /dev1/oracle/dbs/arch/arch000074.arc
     ORA-00280: Change 6677 for thread 1 is in sequence #74
     Specify log: {<RET>=suggested | filename | AUTO | CANCEL}

     At this point, apply the archived logs as requested. Eventually Oracle
     will encounter redo to be applied to the non-existent datafile. The
     recovery session will exit with the following message, and will return
     the user to the Server Manager prompt:

     ORA-00283: Recovery session canceled due to errors
     ORA-01244: unnamed datafile(s) added to controlfile by media recovery
     ORA-01110: data file 5: '/dev1/oracle/dbs/testtbs.dbf'

  4. Recreate the missing datafile. To do this, select the relevant filename
     from v$datafile:

     SVRMGR> select name from v$datafile where file#=5;
     NAME
     -------------------------------------------------------
     UNNAMED0005

     Now recreate the file:

     SVRMGR> alter database create datafile
          2> 'UNNAMED0005'
          3> as
          4> '/dev1/oracle/dbs/testtbs.dbf';

5. Restart recovery

     SVRMGR> recover database using backup controlfile
     ORA-00279: Change 6747 generated at 09/24/97 16:57:18 needed for thread 1
     ORA-00289: Suggestion : /dev1/oracle/dbs/arch/arch000079.arc
     ORA-00280: Change 6747 for thread 1 is in sequence #79
     Specify log: {<RET>=suggested | filename | AUTO | CANCEL}

     Apply archived logs as requested. Prior to Oracle8, recovery must apply
     the complete log which was current at the time of the datafile creation
     (in the above example, this would be log sequence 79). A recovery to a
     point in time before the end of this log would result in errors:

     ORA-01196: file 1 is inconsistent due to a failed media recovery session
     ORA-01110: data file 1: '/dev1/oracle/dbs/systbs.dbf'

     If this happens, re-recover the database and ensure that the complete log
     is applied (plus any further redo if required). This limitation does
     not exist from Oracle 8.0+.

     Eventually, Oracle will request the archived log corresponding to the
     current online log. It does this because the (backup) controlfile has no
     knowledge of the current log sequence. If an attempt is made to apply the
     suggested log, the recovery session will exit with the following message:

     ORA-00308: cannot open archived log '/dev1/oracle/dbs/arch/arch000084.arc'
     ORA-07360: sfifi: stat error, unable to obtain information about file.
     SVR4 Error: 2: No such file or directory

     At this stage, simply restart the recovery session and apply the current
     online log. The best way to do this is to try applying the online redo
     logs one by one until Oracle completes media recovery:

     SVRMGR> recover database using backup controlfile
     ORA-00279: Change 6763 generated at 09/24/97 16:57:59 needed for thread 1
     ORA-00289: Suggestion : /dev1/oracle/dbs/arch/arch000084.arc
     ORA-00280: Change 6763 for thread 1 is in sequence #84
     Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
     /dev1/oracle/dbs/log2.dbf
     Log applied.
     Media recovery complete.

6. Open the database

SVRMGR> alter database open resetlogs;

The resetlogs option must be chosen to resynchronize the controlfile.

NOTES:

These techniques can be used whether the database was closed either cleanly or uncleanly (aborted).
If the database is recovered using an incomplete recovery technique (either time-based, cancel-based, or change-based), and is recovered to a point in time before the datafile was originally created, any references to that datafile will be removed from the database when the database is opened.

Oracle handles this situation as follows:

The 'alter database create datafile....' command creates a reference in the controlfile for the datafile.
Incomplete recovery terminates before applying redo that would create a corresponding row for the datafile in the file$ dictionary table.
When the database is opened, Oracle detects an inconsistency between file$

      and the controlfile and resolves in favour of file$, deleting the entry
      from the controlfile.

c) It may be possible to recover the datafile using this technique even if the

database is not in archivelog mode. However, this relies on the required redo being available in the online redo logs.

Good luck ...

"Au revoir" from Paris

Christophe Brault
DBA Oracle Received on Wed Jun 06 2001 - 07:03:44 CDT