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RMAN Recovery
Catalog Tips
Oracle Tips by Burleson Consulting |
RMAN uses a recovery catalog; however, you can
use RMAN without a catalog from just the data stored in the control
files, but you are restricted to a subset of RMANs capabilities in
this mode. The recovery catalog contains information on the following:
* Data file and archive log backup sets and
pieces
* Data file copies
* Archived redo logs and copies of them
* Tablespaces and data files at the target
database
* Named, user-created sequences of commands
called stored scripts
* incarnation data
* backup history
metadata
* redo log switch history
It is a good practice to maintain a small
database strictly for the recovery catalog and perhaps the Enterprise
Manager catalog files. The recovery catalog should be resynchronized with all
remote databases on a periodic basis. If you don?t use a catalog you
cannot do the following:
* Point-in-time recover
* Use stored scripts
* Recovery if a control file is not available.
RMAN creates backup sets that consist of
backup pieces. Backup pieces are parts of the backup set at a size
that is predetermined and usually based on backup media capacity of
operating system file size limitations. Backup sets can be written to
disk or secondary storage, can include a backup control file, and can
span multiple OS files (pieces). Backup devices that are supported on
your system are cataloged in the v$backup_device dynamic performance
table.
The recovery catalog contains RMAN metadata.
The recovery catalog is updated after you take a backup, when
there is a log switch, and when you change a tablespace or datafile.
RMAN backup sets that contain archive logs are
called, appropriately enough, archivelog backup sets. With Oracle8 you
cannot write archive logs directly to tape, but a job can be scheduled
using RMAN to back archive log backup sets to tape or other storage.
RMAN produces either full or incremental
backups. A full backup is a backup of one or more data files that
contains all blocks of the data file(s) that have been modified or
changed. Full backups can be created out of:
* Data files
* Data file copies
* Tablespaces (all data files for a
tablespace)
* Archive logs
* Control files (current or backups)
* Entire databases
An incremental backup is a backup of one or
more files and contains only blocks that have been modified. However,
only complete control files are backed up in either incremental or
full backups. Incremental backups can be made of:
* Data files
* Tablespaces
* Databases
The incremental backup allows leveling of
backups. Each level is denoted by an integer value, with the level of
backup meaning that any blocks changed since the last incremental
backup at this level will be backed up the next time this level is
specified. This allows levels to be set based on time frames; for
example, 0 being a monthly full, 1 being a once-a-week incremental,
and 2 being a daily incremental. Of course, this also leads to
complicated rotation of tapes or backup media, taking us back to the
good old towers-of-Hanoi backup scenario nightmares.
RMAN also allows for image copies of data
files, archive logs, or control files. Image copies can only be made
to disk and cannot contain multiple files.
RMAN allows report generation. Reports can be
generated based on:
* What files need backup.
* What files haven?t been backed up recently.
* What backup files can be deleted.
Each backup set can be associated with a tag
that can be used to identify it in subsequent operations. The tag
doesn?t have to be unique. RMAN selects the most recent backup set in
the case of backup sets with duplicate tags.
RMAN works against running or shutdown
databases whether they are in archive log mode or not. However, if the
database is not in archive log mode the entire database can only be
backed up if it was shut down cleanly. Tablespaces can only be backed
up in NOARCHIVELOG mode if they are off-line normal. There are no
restrictions of this type on databases in ARCHIVELOG mode.
RMAN automatically detects corruptions and
logs these in v$backup_corruption and v$copy_corruption dynamic
performance tables. Corrupt blocks are still backed up.
Installing the RMAN Recovery Catalog
The recovery catalog should be owned by a user with the
resource role grant. I suggest a user in a small database dedicated to
system administration functions such as the RMAN catalog and
Enterprise Manager catalog. Create a tablespace for use by the
RMAN user and assign that as the user?s default tablespace with
unlimited quota. For example, if we wanted our user to be named rman_dba, the steps would be as follows:
sqlplus
system/manager
SQL>CREATE TABLESPACE rman_data DATAFILE 'file_spec' DEFAULT STORAGE
(clause);
SQL>CREATE USER rman_dba IDENTIFIED BY rman_dba
2: DEFAULT TABLESPACE rman_data
3: TEMPORARY TABLESPACE temp
4: QUOTA UNLIMITED ON rman_data;
SQL>GRANT RESOURCE,CONNECT TO rman_dba;
SQL>CONNECT rman_dba/rman_dba
SQL> @$ORACLE_HOME/rdbms/admin/catrman.sql
Once the catalog is built, the recovery
manager can be utilized. The command is either rman, rman80, or RMAN80
depending on your operating system. There are literally dozens of
commands for use with the RMAN facility. I suggest reviewing the
Oracle8i Server Backup and Recovery Guide, Release 8.1.5 (or most
current release) (Oracle Corporation, 1999) before using RMAN.
The following are some example scenarios
showing how the commands can be made into scripts.
Connection to rman in UNIX on early versions
can be tricky. On some UNICES the double quote (?) character has to be
escaped, and you need to use the double quotes to log into rman (at
least on early versions). Assuming the database to be backed up is
ORTEST1 with a TNS alias of ORTEST1, the user is as specified earlier,
and the catalog database is ORRMAN, the connection to RMAN for the
user SYSTEM password MANAGER would look like this:
$ rman
ORTEST1\ system/manager@ORTEST1 rcvcat "rman_dbo/rman_dbo@ORRMAN\"
Intuitive, isn?t it? A sample session from
Recovery Manager (RMAN) is shown next.
The target database service name in the
?tnsnames.ora? file is ?ORTEST1.? The recovery catalog database
service name in the ?tnsnames.ora? file is ?ORRMAN.?
% cd $ORACLE_HOME/rdbms/admin
% sqlplus
sys/change_on_install@ORRMAN
SQL> grant connect, resource to RMAN_DBA identified by RMAN_DBA;
Grant succeeded.
SQL> connect rman/rman@ORRMAN
Connected.
SQL> @catrman.sql
SQL> exit
%
% rman 'target sys/change_on_install@ORTEST1 rcvcat
rman/rman@ORRMAN'
Recovery Manager: Release 8.0.2.0.0 - Beta
RMAN-06005: connected to target database: ORTEST1
RMAN-06008: connected to recovery catalog database
RMAN> register database;
RMAN-08006: database registered in recovery catalog
RMAN-08002: starting full resync of recovery catalog
RMAN-08004: full resync complete
RMAN> run
2> {
3> allocate channel c1 type disk;
4> backup full format '/oracle16/ORTEST1/amin/backup/backup%s%p'
(database);
5> }
RMAN-08030: allocated channel: c1
RMAN-08500: channel c1: sid=12 devtype=DISK
RMAN-08008: channel c1: started datafile backupset
RMAN-08502: set_count=9 set_stamp=280246639
RMAN-08011:
channel c1: including current controlfile in backupset
RMAN-08010: channel c1: including datafile number 1 in backupset
RMAN-08010: channel c1: including datafile number 2 in backupset
.
.
.
RMAN-08010: channel c1: including datafile number 11 in backupset
RMAN-08010: channel c1: including datafile number 12 in backupset
RMAN-08013: channel c1: piece 1 created
RMAN-08503: piece handle=/oracle16/ORTEST1/admin/backup/backup91
comment=NONE
RMAN-08003: starting partial resync of recovery catalog
RMAN-08005: partial resync complete
RMAN-10030: RPC call appears to have failed to start on channel
default
RMAN-10036: RPC call ok on channel default
RMAN-08031: released channel: c1
RMAN> exit
Incomplete restore scenario
The following shows the scenario for an
incomplete recovery. The following scenario assumes that:
* You wish to do an incomplete recovery due to
an application error that was made at a specific time.
* There are three tape drives.
* You are using a recovery catalog.
TIP: It is highly advisable to back up the
database immediately after opening the database resetlogs.
The following script restores and recovers the
database to the time immediately before the user error occurred. The
script does the following:
* Starts the database mount and restricts
connections to DBA-only users.
* Restores the database files (to the original
locations).
* Recovers the data files by either using a
combination of incremental backups and redo or just redo. Recovery
Manager will complete the recovery when it reaches the transaction
from the time specified.
* Opens the database resetlogs.
Oracle recommends that you backup your
database after the resetlogs (this is not shown in the example).
Ensure that you set your NLS_LANG and
NLS_DATE_FORMAT environment variables. You can set these to whatever
you wish?the date format of the following example is the standard date
format used for recovery, e.g., for UNIX (csh):
> setenv
NLS_LANG AMERICAN
> setenv NLS_DATE_FORMAT 'YYYY-MM-DD:hh24:mi:ss'
Next, start up Server Manager:
SVRMGR>
connect internal
Connected.
SVRMGR> startup mount restrict
SVRMGR>exit
# rman target internal/knl@prod1 rcvcat rman/rman@rcat cmdfile
case2.rcv
run {
# The 'set until time' command is for all commands executed
# between the { and } braces. Means both restore and recover
# will both be relative to that point in time.
# Note that Recovery Manager uses the Recovery Catalog to,
# determine the structure of the database at that time, and
# restore it.
#
set until time '1997-06-23:15:45:00';
#
allocate channel t1 type 'SBT_TAPE';
allocate channel t2 type 'SBT_TAPE';
allocate channel t3 type 'SBT_TAPE';
#
restore
(database);
#
# There is no need to manually catalog logs before recovery,
# as Recovery Manager does catalog resync from the current
# control file.
#
recover
database;
#
sql 'alter database open resetlogs';
The preceding scenarios are just examples of
how to use the recovery manager. Please consult your manual before
attempting to use the facility for production work. The RMAN readme
file contains valuable insights into RMAN use and has several
additional scenarios.
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