How to Recover an Oracle Database Having Added a Datafile Since Last Backup

Posted by PDSERVICE on Apr 06, 2020 In

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HOW TO RECOVER A DATABASE HAVING ADDED A DATAFILE SINCE THE LAST BACKUP

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This bulletin outlines the steps required in performing database recovery

having added a datafile to the database since the last backup was taken.

Section A is applicable to Oracle release 7.x. Section B applies only to

Oracle releases 7.3.x and above.

PLEASE READ THROUGH ALL STEPS AND WARNINGS BEFORE ATTEMPTING TO USE THIS

BULLETIN.

A. Current controlfile, backup of datafile exists (Oracle release 7.x)

===================================================================

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).

1. 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.

2. Mount the database

3. Create a new datafile using the 'ALTER DATABASE CREATE DATAFILE' command.

a. The datafile can be created with the same name as the original

file. For example,

SQLDBA> alter database create datafile

2> '/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> '/oracle/dbs/testtbs.dbf'

3> as

4> '/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 : /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.

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 and above)

=======================================================================

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).

NOTE : 'svrmgrl' has been replaced by SQL*Plus starting from Oracle8i

So the 'SVRMGR>' prompt is than replaced by 'SQL>'

1. 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.

2. Mount the database

3. 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 : /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: '/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> '/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 : /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: '/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 '/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 : /oracle/dbs/arch/arch000084.arc

ORA-00280: Change 6763 for thread 1 is in sequence #84

Specify log: {<RET>=suggested | filename | AUTO | CANCEL}

/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:

======

a) These techniques can be used whether the database was closed either

cleanly or uncleanly (aborted).

b) 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 favor 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.

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How to Recover an Oracle Database Having Added a Datafile Since Last Backup

How to Recover an Oracle Database Having Added a Datafile Since Last Backup