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How to extract controlfiles, datafiles, and archived logs from SMR backupsets without using RMAN

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How to extract controlfiles, datafiles, and archived logs from

SMR backupsets without using RMAN

Introduction:

When using RMAN to restore objects (datafiles, controlfiles, or archivelogs)

from backupsets, the object restore can be driven from the recovery catalog

or the target database controlfile. This note explains how to extract

objects from backupsets when the recovery catalog and controlfiles have been

lost. In this scenario, you effectively perform. the RMAN functions through

PL/SQL procedure calls

Contents:

1. Prerequisites

2. Extracting the controlfile from a backupset

3. Extracting datafiles from a backupset

4. Applying incrementals

5. Extracting archivelogs from a backupset

6. A typical scenario

7. Errors

8. Things to be done

1. Prerequisites

The customer must have a knowledge of the contents of backupsets i.e. what

they contain, when the backups were created, and the type of backups. Ideally

they should have logs of the RMAN backup sessions that produced the

backupsets.

Note that the following anonymous PL/SQL blocks are run on the instance of

the database being recovered (the 'target'). The instance must be at least

started (once the controlfile has been restored the database can also be

mounted). Anonymous blocks can be executed in this manner as long as they

call only 'fixed' packages. The DBMS_BACKUP_RESTORE packages are fixed.

IMPORTANT: All the anonymous blocks must be executed by SYS or a user

who has execute privilege on SYS.DBMS_BACKUP_RESTORE

2. Extracting the controlfile from a backupset

The first stage is to extract the controlfile from a backupset. This is

achieved by making use of the following SYS.DBMS_BACKUP_RESTORE packaged

functions & procedures:

FUNCTION deviceAllocate - allocates a device for sequential I/O

PROCEDURE restoreSetDataFile - begins a restore conversation

PROCEDURE restoreControlfileTo - specifies the controlfile destination

PROCEDURE restoreBackupPiece - performs the restore

PROCEDURE deviceDeallocate - deallocates the I/O device

The following anonymous block can be created and executed to restore a

controlfile from a backupset. Before executing it, you MUST edit the block

as follows:

a. The filetable PL/SQL table entries must reflect the backuppieces

comprising the backupset

b. The v_maxPieces variable must reflect the number of backuppieces

comprising the backupset

c. The call to restoreControlfileTo must specify the correct controlfile

path & filename

IMPORTANT: The latest backup of the controlfile should be restored. Because

recovery (using backup controlfile) will be performed manually,

the recovering session will need to start applying redo from

the current log sequence AT THE TIME OF THE CONTROLFILE BACKUP.

Thus, to take advantage of incremental backups, restore a

controlfile taken along with the incremental backups, thus

reducing the amount of redo required during recovery.

DECLARE

v_dev varchar2(50); -- device type allocated for restore

v_done boolean; -- has the controlfile been fully extracted yet

type t_fileTable is table of varchar2(255)

index by binary_integer;

v_fileTable t_fileTable; -- Stores the backuppiece names

v_maxPieces number:=1; -- Number of backuppieces in backupset

BEGIN

-- Initialise the filetable & number of backup pieces in the backupset

-- This section of code MUST be edited to reflect the customer's available

-- backupset before the procedure is compiled and run. In this example, the

-- backupset consists of 4 pieces:

v_fileTable(1):='fulldb_s15_p1';

v_fileTable(2):='fulldb_s15_p2';

v_fileTable(3):='fulldb_s15_p3';

v_fileTable(4):='fulldb_s15_p4';

v_maxPieces:=4;

-- Allocate a device. In this example, I have specified 'sbt_tape' as I am

-- reading backuppieces from the media manager. If the backuppiece is on disk,

-- specify type=>null

v_dev:=sys.dbms_backup_restore.deviceAllocate(type=>'sbt_tape',

ident=>'t1');

-- Begin the restore conversation

sys.dbms_backup_restore.restoreSetDatafile;

-- Specify where the controlfile is to be recreated

sys.dbms_backup_restore.restoreControlfileTo(cfname=>'/support2/OFA_V804/u1/oradata/dbs/ctrl1V804.ctl');

-- Restore the controlfile

FOR i IN 1..v_maxPieces LOOP

sys.dbms_backup_restore.restoreBackupPiece(done=>v_done,

handle=>v_fileTable(i),

params=>null);

IF v_done THEN

GOTO all_done;

END IF;

END LOOP;

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