RMAN Frequently Asked
Questions
1. What is RMAN ?
Recovery
Manager (RMAN) is a utility that can manage your entire Oracle backup and
recovery activities.
Which Files must be backed up?
Database
Files (with RMAN)
Control Files (with RMAN)
Offline Redolog Files (with RMAN)
INIT.ORA (manually)
Password Files (manually)
2.
When you take a hot backup putting Tablespace in begin backup mode, Oracle
records SCN # from header of a database file. What happens when you issue
hot backup database in RMAN at block level backup? How does RMAN mark the
record that the block has been backed up ? How does RMAN know what blocks
were backed up so that it doesn't have to scan them again?
In 11g, there is Oracle Block Change
Tracking feature. Once enabled; this new 10g feature records the modified
since last backup and stores the log of it in a block change tracking file.
During backups RMAN uses the log file to identify the specific blocks that must
be backed up. This improves RMAN's performance as it does not have to scan
whole datafiles to detect changed blocks.
Logging of changed blocks is performed by the CTRW process which is also
responsible for writing data to the block change tracking file. RMAN uses SCNs
on the block level and the archived redo logs to resolve any inconsistencies in
the datafiles from a hot backup. What RMAN does not require is to put the
tablespace in BACKUP mode, thus freezing the SCN in the header. Rather, RMAN
keeps this information in either your control files or in the RMAN repository (i.e.,
Recovery Catalog).
3. What are the Architectural
components of RMAN?
1.RMAN executable
2.Server processes
3.Channels
4.Target database
5.Recovery catalog database (optional)
6.Media management layer (optional)
7.Backups, backup sets, and backup pieces
4. What are Channels?
A channel is an RMAN server process
started when there is a need to communicate with an I/O device, such as a disk
or a tape. A channel is what reads and writes RMAN backup files. It is through
the allocation of channels that you govern I/O characteristics such as:
- Type
of I/O device being read or written to, either a disk or an sbt_tape
- Number
of processes simultaneously accessing an I/O device
- Maximum
size of files created on I/O devices
- Maximum
rate at which database files are read
- Maximum
number of files open at a time
5. Why is the catalog optional?
Because RMAN manages backup and
recovery operations, it requires a place to store necessary information about
the database. RMAN always stores this information in the target database
control file. You can also store RMAN metadata in a recovery catalog schema
contained in a separate database. The recovery catalog
schema must be stored in a database other than the target database.
6. What does complete RMAN
backup consist of ?
A backup
of all or part of your database. This results from issuing an RMAN backup
command. A backup consists of one or more backup sets.
7. What is a Backup set?
A logical grouping of backup files -- the
backup pieces -- that are created when you issue an RMAN backup command. A
backup set is RMAN's name for a collection of files associated with a backup. A
backup set is composed of one or more backup pieces.
8. What is a Backup piece?
A physical binary file created by RMAN during a
backup. Backup pieces are written to your backup medium, whether to disk or
tape. They contain blocks from the target database's datafiles, archived redo
log files, and control files. When RMAN constructs a backup piece from
datafiles, there are a several rules that it follows:
A datafile cannot
span backup sets
A datafile can
span backup pieces as long as it stays within one backup set
Datafiles and
control files can coexist in the same backup sets
Archived redo log
files are never in the same backup set as datafiles or control files RMAN is
the only tool that can operate on backup pieces. If you need to restore a file
from an RMAN backup, you must use RMAN to do it. There's no way for you to
manually reconstruct database files from the backup pieces. You must use RMAN
to restore files from a backup piece.
9. What are the benefits of
using RMAN?
1. Incremental backups that only copy
data blocks that have changed since the last backup.
2. Tablespaces are not put in backup mode, thus there is noextra redo log generation
during online backups.
3. Detection of corrupt blocks during backups.
4. Parallelization of I/O operations.
5. Automatic logging of all backup and recovery operations.
6. Built-in reporting and listing commands.
The PREVIEW option of the RESTORE
command allows you to identify the backups required to complete a specific
restore operation. The output generated by the command is in the same format as
the LIST command. In addition the PREVIEW SUMMARY command can be used to
produce a summary report with the same format as the LIST SUMMARY command. The
following examples show how these commands are used:
# Spool output to a log file
SPOOL LOG TO c:\oracle\rmancmd\restorepreview.lst;
# Show what files will be used to
restore the SYSTEM tablespace’s datafile
RESTORE DATAFILE 2 PREVIEW;
# Show what files will be used to
restore a specific tablespace
RESTORE TABLESPACE users PREVIEW;
# Show a summary for a full database
restore
RESTORE DATABASE PREVIEW SUMMARY;
# Close the log file
SPOOL LOG OFF;
11. Where should the catalog be created?
The recovery catalog to be used by
rman should be created in a separate database other than the target database.
The reason been that the target database will be shutdown while datafiles are
restored.
12. How many times does oracle ask before
dropping a catalog?
The default is two times one for the
actual command, the other for confirmation.
13. How to view the current defaults for the
database.
RMAN> show all;
RMAN configuration parameters are:
CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 3 DAYS;
CONFIGURE BACKUP OPTIMIZATION OFF; # default
CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default
CONFIGURE CONTROLFILE AUTOBACKUP OFF; # default
CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO ‘%F’; # default
CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default
CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
CONFIGURE MAXSETSIZE TO UNLIMITED; # default
CONFIGURE ARCHIVELOG DELETION POLICY TO NONE; # default
CONFIGURE SNAPSHOT CONTROLFILE NAME TO ‘/u02/app/oracle/product/10.1.0/db_1/dbs/snapcf_test.f’;
# default
14. Backup the database.
run
{
backup incremental level $level ${level_keyword}
tag INC${target_db}_$level database include current controlfile;
backup archivelog all not backed up 1 times delete input;
}
15. How to resolve the ora-19804 error
Basically this error is because of
flash recovery area been full. One way to solve is to increase the space
available for flashback database.
sql>ALTER SYSTEM SET
DB_RECOVERY_FILE_DEST_SIZE=5G; –It can be set to K,M or G.
rman>backup database;
……………….
channel ORA_DISK_1: specifying datafile(s) in backupset
including current controlfile in backupset
including current SPFILE in backupset
channel ORA_DISK_1: starting piece 1 at 04-JUL-05
channel ORA_DISK_1: finished piece 1 at 04-JUL-05
piece
handle=/u02/app/oracle/flash_recovery_area/TEST/backupset/2005_07_04/o1_mf_ncsnf_TAG20050704T205840_1dmy15cr_.bkp
comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03
Finished backup at 04-JUL-05
Oracle Flashback
After taking a back up resync the
database.
Restoring the whole database.
run {
shutdown immediate;
startup mount;
restore database;
recover database;
alter database open;
}
16. What are the various reports available with
RMAN
rman>list backup;
rman> list archive;
17. What does backup incremental level=0 database
do?
Backup database level=0 is a full
backup of the database. rman>>backup incremental level=0 database;
You can also use backup full database;
which means the same thing as level=0;
18. What is the difference between DELETE INPUT
and DELETE ALL command in backup?
Generally speaking LOG_ARCHIVE_DEST_n
points to two disk drive locations where we archive the files, when a command
is issued through rman to backup archivelogs it uses one of the location to
backup the data. When we specify delete input the location which was backedup
will get deleted, if we specify delete all all log_archive_dest_n will get
deleted.
DELETE all applies only to archived
logs. delete expired archivelog all;
19. How do I backup archive log?
In order to backup archivelog we have
to do the following:-
run
{
allocate channel t1 type 'SBT_TAPE';
delete noprompt archivelog until time = 'sysdate-3/24';
delete noprompt obsolete;
release channel t1;
}
20.
How do I do a incremental backup after a base backup?
run
{
backup incremental level $level ${level_keyword}
tag INC${target_db}_$level database include current controlfile;
backup archivelog all not backed up 1 times delete input;
}
21. In
catalog database, if some of the blocks are corrupted due to system crash, How will
you recover?
using RMAN BLOCK RECOVER command
22. You
have taken a manual backup of a datafile using o/s. How RMAN will know about
it?
You have to catalog that manual backup in RMAN's repository by command
RMAN> catalog datafilecopy '/DB01/BACKUP/users01.dbf';
restrictions:
> Accessible on disk
> A complete image copy of a single file
23. Where
RMAN keeps information of backups if you are using RMAN without Catalog?
RMAN keeps information of backups in the control file.
CATALOG vs NOCATALOG
the difference is only who maintains the backup records like when is the
last successful backup incremental differential etc.
In CATALOG mode another database (TARGET database) stores all the information.
In NOCATALOG mode controlfile of Target database is responsible.
24. How
do you see information about backups in RMAN?
RMAN> List Backup;
Use this SQL to check
SQL> SELECT sid totalwork sofar FROM v$session_longops WHERE sid 153;
Here give SID when back start it will show SID
25. How
RMAN improves backup time?
RMAN backup time consumption is very less than compared to regular
online backup as RMAN copies only modified blocks
26. What
is the advantage of RMAN utility?
Central Repository
Incremental Backup
Corruption Detection
Advantage over tradition backup system:
1). copies only the filled blocks i.e. even if 1000 blocks is allocated
to datafile but 500 are filled with data then RMAN will only create a backup
for that 500 filled blocks.
2). incremental and accumulative backup.
3). catalog and no catalog option.
4). detection of corrupted blocks during backup;
5). can create and store the backup and recover scripts.
6). increase performance through automatic parallelization( allocating
channels) less redo generation.
27. List
the encryption options available with RMAN?
RMAN offers three encryption modes: transparent mode, password mode and
dual mode.
28. What
are the steps required to perform in $ORACLE_HOME for enabling the RMAN backups
with netbackup or TSM tape library software?
I can explain what are all the steps to take a rman backup with TSM tape
library as follows
1.Install TDPO (default path /usr/tivoli/tsm/client/oracle/)
2.Once u installed the TDPO automatically one link is created from TDPO directory
to /usr/lib.Now we need to Create soft link between OS to ORACLE_HOME
ln -s /usr/lib/libiobk64.a $ORACLE_HOME/lib/libobk.a(very imporatant)
3.Uncomment and Modify tdpo.opt file which in
/usr/tivoli/tsm/client/oracle/bin/tdpo.opt as follows
DSMI_ORC_CONFIG /usr/Tivoli/tsm/client/oracle/bin64/dsm.opt
DSMI_LOG /home/tmp/oracle
TDPO_NODE backup
TDPO_PSWDPATH /usr/tivoli/tsm/client/oracle/bin64
4.create dsm.sys file in same path and add the entries
SErvername <Server name >
TCPPort 1500
passwordacess prompt
nodename backup
enablelanfree yes
TCPSERVERADDRESS <Server Address>
5.Create dsm.opt file add an entry
SErvername <Server name >
6.Then take backup
RMAN>run
{
allocate channel t1 type 'sbt_tape' parms
'ENV (TDPO_OPTFILE /usr/tivoli/tsm/client/oracle/bin64/tdpo.opt)';
backup database include current controlfile;
release channel t1;
}
29. What
is the significance of incarnation and DBID in the RMAN backups?
When you have multiple databases you have to set your DBID (Database Id)
which is unique to each database. You have to set this before you do any
restore operation from RMAN.
There is possibility that incarnation may be different of your database.
So it is advised to reset to match with the current incarnation. If you run the
RMAN command ALTER DATABASE OPEN RESETLOGS then RMAN resets the
target database automatically so that you do not have to run RESET
DATABASE. By resetting the database RMAN considers the new incarnation as the
current incarnation of the database.
30. List
at least 6 advantages of RMAN backups compare to traditional hot backups?
RMAN has the following advantages over Traditional backups:
1. Ability to perform INCREMENTAL backups
2. Ability to Recover one block of datafile
3. Ability to automatically backup CONTROLFILE and SPFILE
4. Ability to delete the older ARCHIVE REDOLOG files, with the new one's
automatically.
5. Ability to perform backup and restore with parallelism.
6. Ability to report the files needed for the backup.
7. Ability to RESTART the failed backup, without starting from beginning.
8. Much faster when compared to other TRADITIONAL backup strategies.
31. How
do you enable the autobackup for the controlfile using RMAN?
issue command at rman prompt.....
RMAN> configure controlfile autobackup on;
also we can configure controlfile backup format......
RMAN> configure controlfile autobackup format for device type disk to
2> '$HOME/BACKUP/RMAN/ F.bkp';
$HOME/BACKUP/RMAN/ this can be any desired
location.
32. How
do you identify what are the all the target databases that are being backed-up with
RMAN database?
You don’t have any view to identify whether it is backed up or not . The
only option is connect to the target database and give list backup this will
give you the backup information with date and timing.
33. What
is the difference between cumulative incremental and differential incremental backups?
Differential backup: This is the default type of
incremental backup which backs up all blocks changed after the most recent
backup at level n or lower.
Cumulative backup: Backup all blocks changed after
the most recent backup at level n-1 or lower.
34. How
do you identify the block corruption in RMAN database? How do you fix it?
using v$block_corruption view u can find which blocks corrupted.
Rman>> block recover datafile <fileid> block <blockid>;
Using the above statement u recover the corrupted blocks.
First check whether the block is corrupted or not by using this command
sql>select file# block# from v$database_block_corruption;
file# block
2 507
the above block is corrupted...
conn to Rman
To recover the block use this command...
Rman>blockrecover dataile 2 block 507;
the above command recover the block 507
Now just verify it.....
Rman>blockrecover corruption list;
35. How
do you clone the database using RMAN software? Give brief steps? When do you
use crosscheck command?
Check whether backup pieces proxy copies or disk copies still exist.
Two commands available in RMAN to clone database:
1) Duplicate
2) Restore.
36. What
is the difference between obsolete RMAN backups and expired RMAN backups?
The term obsolete does not mean the same as expired. In short obsolete means "not needed " whereas expired means
"not found."
37. List
some of the RMAN catalog view names which contain the catalog information?
RC_DATABASE_INCARNATION RC_BACKUP_COPY_DETAILS
RC_BACKUP_CORRUPTION
RC_BACKUP-DATAFILE_SUMMARY to name a few
38. What
is db_recovery_file_dest ? When do you need to set this value?
If Database Flashback option is on then use this option.
39. How
do you setup the RMAN tape backups?
RMAN Target /
run
{
Allocate channel ch1 device type sbt_tape maxpiecesize 4g
Format' D_ U_ T_ t';
sql 'alter system switch logfile';
Backup database;
backup archivelog from time 'sysdate-7';
Backup Format ' D_CTLFILE_P_ U_ T_ t' Current controlfile;
release channel ch1;
}
This is backup script for Tivoli Backup Server
40. How
do you install the RMAN recovery catalog?
Steps to be followed:
1) Create connection string at catalog database.
2) At catalog database create one new user or use existing user and give
that user a recovery_catalog_owner privilege.
3)Login into RMAN with connection string
a) export ORACLE_SID
b) rman target catalog @connection string
4) rman> create catalog;
5) register database;
41. When
do you recommend hot backup? What are the pre-reqs?
Database must be Archivelog Mode
Archive Destination must be set and LOG_ARCHIVE_START TRUE (EARLIER VERSION
BEFORE 10G)
If you go through RMAN then
CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default
CONFIGURE BACKUP OPTIMIZATION OFF; # default
CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default
CONFIGURE CONTROLFILE AUTOBACKUP ON;
CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO
'/u01/oracle/autobackup/ F';
CONFIGURE DEVICE TYPE DISK PARALLELISM 2BACKUP TYPE TO BACKUPSET; #
default
CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
CONFIGURE MAXSETSIZE TO UNLIMITED; # default
CONFIGURE ENCRYPTION FOR DATABASE OFF; # default
CONFIGURE ENCRYPTION ALGORITHM 'AES128'; # default
CONFIGURE ARCHIVELOG DELETION POLICY TO NONE; # default
CONFIGURE SNAPSHOT CONTROLFILE NAME TO
'/u01/app/oracle/product/10.2.0/db_2/dbs/snapcf_dba.f'; # default
42. What
is the difference between physical and logical backups?
In Oracle Logical Backup is "which is taken using either
Traditional Export/Import or Latest Data Pump". Where as Physical backup
is known "when you take Physical O/s Database related Files as
Backup".
43. What
is RAID? What is RAID0? What is RAID1? What is RAID 10?
RAID: It is a redundant array of independent disk
RAID0: Concatenation and stripping
RAID1: Mirroring
44. What
are things which play major role in designing the backup strategy?
I Believe in designing a good backup strategy it will not only be simply
backup but also a contingency plan. In this case you should consider the
following:
1. How long is the allowable down time during recovery? - If short you
could consider using dataguard.
2. How long is the backup period? - If short I would advise to use RMAN
instead of user managed backup.
3. If limited disk space for backup never use user managed backup.
4. If the database is large you could consider doing full rman backups
on a weekend and do a incremental backup on a weekday.
5. Schedule your backup on the time where there is least database
activity this is to avoid resource huggling.
6. Backup script should always be automized via scheduled jobs. This way
operators would never miss a backup period.
7. Retention period should also be considered. Try keeping atleast 2
full backups. (current and previous backup).
Cold backup: shutdown the database and copy the datafiles with the help
of
O.S. command. this is simply copying of datafiles just like any other
text file copy.
Hot backup: backup process starts even though database in running. The process
to take a hot backup is
1) sql> alter database begin backup;
2) copy the datafiles.
3) after copying
sql> alter database end backup;
Begin backup clause will generate the timestamp. it'll be used in backup
consistency i.e. when begin backup pressed it'll generate the timestamp. During
restore database will restore the data from backup till that timestamp and remaining
backup will be recovered from archive log.
45. What
is hot backup and what is cold backup?
Hot backup when the database is online cold backup is taken during shut
down period
46. How do you test that your recovery was
successful?
SQL> SELECT count(*) FROM flashback_table;
47. How do you backup the Flash Recovery
Area?
A:RMAN> BACKUP RECOVERY FILES;
The files on disk that have not previously been backed up will be backed
up. They are full and incremental backup sets,
control file auto-backups, archive logs and datafile copies.
48. How to enable Fast Incremental Backup
to backup only those data blocks that have changed?
A:SQL> ALTER DATABASE enable BLOCK CHANGE TRACKING;
49. How do you set the flash recovery area?
A:SQL>
ALTER SYSTEM SET db_recovery_file_dest_size = 100G;SQL> ALTER SYSTEM SET
db_recovery_file_dest = ‘/u10/oradata/school’;
50. How can you use the CURRENT_SCN column
in the V$DATABASE view to obtain the currentSCN?
A:SQL> SELECT current_scn FROM v$database;
51. You have taken a manual backup of a
datafile using o/s. How RMAN will know about it?
You have to catalog that manual backup in RMAN's repository by command
RMAN> catalogdatafilecopy '/DB01/BACKUP/users01.dbf';
restrictions:> Accessible on disk> A complete image copyof a
single file
52. In catalog database, if some of the
blocks are corrupted due to system crash, How will you recover?
using RMAN BLOCK RECOVER command
53. List advantages of RMAN backups compare
to traditional hot backups?
RMAN has the following advantages over Traditional backups:
1. Ability to perform INCREMENTALbackups
2. Ability to Recover one block of datafile
3. Ability to automatically backup CONTROLFILEand SPFILE
4. Ability to delete the older ARCHIVE REDOLOG files
54. How do you identify the expired,
active, obsolete backups? Which RMAN command you use?
Use command:
Rman > crosscheck backup;
Rman > crosscheck archivelog all;
Rman > listbackup;
Rman > list archive logall
55. How do you enable the autobackup for
the controlfile using RMAN?
RMAN> configure controlfile autobackup on;
also we can configurecontrolfile backup format......
RMAN> configure control file auto backup format for device type disk
56. How do you identify what are the all
the target databases that are being backed-up with RMAN database?
You don’t have any view to identify whether it is backed up or not . The
only option is connect to the target database and give list backup, this will
give you the backup information with date and timing
57. What is the difference between
cumulative incremental and differential incremental backups?
Differential backup: This is the default type of incremental backup
which backs up all blocks changed after the most recent backup at level n or
lower.
Cumulative backup: Backup all blocks changed after the most recent
backup at level n-1 or lower
58. Explain how to setup the physical stand
by database with RMAN?
$ Export ORACLE_SID=TEST $ rman target /
RMAN> show all;
Using target database controlfile instead of recovery catalog RMAN
configuration parameters are:
CONFIGURE RETENTIONPOLICY TO
RECOVERY WINDOW OF 1 DAYS;
CONFIGURE BACKUP OPTIMIZATION
59. What is auxiliary channel in RMAN? When
do you need this?
An auxiliary channel is a link to auxiliary instance. If you do not have
automatic channels configured, then before issuing the DUPLICATE command,
manually allocate at least one auxiliary channel with in the same RUN command.
60. What is backup set?
RMAN can also store its backups in an RMAN-exclusive format which is
called backup set. A backupset is a collection of backup pieces, each of which
may contain one or more datafile backups
61. What is RMAN and how does one use it?
Recovery Manager (or RMAN) is an Oracle provided utility for backing-up,
restoring and recoveringOracle Databases. RMAN ships with the database server
and doesn't require a separate installation. TheRMAN executable is located in
your ORACLE_HOME/bin directory.
62. What kind of backup are supported by
RMAN?
Backup SetsDatafiles CopiesOS BackupWhat is
the Flash Recovery Area?
A: It is a unified storage location for all recovery-related files and
activities in an Oracle Database. Itincludes Control File, Archived Log Files,
Flashback Logs, Control File Autobackups, Data Files, andRMAN files.
63. How do you define a Flash Recovery
Area?
A: To define a Flash Recovery Area set the following Oracle
Initialization Parameters.
SQL> ALTER SYSTEM SET db_recovery_file_dest_size = 100G;
SQL> ALTER SYSTEM SET db_recovery_file_dest = ‘/u10/oradata/school’;
64. How do you use the V$RECOVERY_FILE_DEST
view to display information regarding the flashrecovery area?
A:SQL> SELECT name, space_limit, space_used,space_reclaimable,
number_of_filesFROM v$recovery_file_dest;
65. How can you display warning messages?
A:SQL> SELECT object_type, message_type,message_level, reason,
suggested_actionFROM dba_outstanding_alerts;
66. How to use the best practice to use
Oracle Managed File (OMF) to let Oracle database to create andmanage the
underlying operating system files of a database?
A:SQL> ALTER SYSTEM SETdb_create_file_dest = ‘/u03/oradata/school’;
SQL> ALTER SYSTEM SETdb_create_online_dest_1 = ‘/u04/oradata/school’;
67. How to enable Fast Incremental Backup
to backup only those data blocks that have changed?
A:SQL> ALTER DATABASE enable BLOCK CHANGE TRACKING;
68. How do you monitor block change
tracking?
A:SQL> SELECT filename, status, bytes FROM v$block_change_tracking;
It shows where the block change-tracking file is located, the status of
it and the size.
69. How do you use the V$BACKUP_DATAFILE
view to display how effective the block change trackingis in minimizing the
incremental backup I/O?
A:SQL> SELECT file#, AVG(datafile_blocks), AVG(blocks_read),AVG
(blocks_read/datafile_blocks), AVG(blocks)FROM v$backup_datafileWHERE
used_change_tracking = ‘YES’ AND incremental_level > 0GROUP BY file#;If the
AVG (blocks_read/datafile_blocks) column is high then you may have to decrease
the timebetween the incremental backups.
70. How do you backup the entire database?
A:RMAN> BACKUP DATABASE;
71. How do you backup an individual
tablespaces?
A:RMAN> CONFIGURE DEFAULT DEVICE TYPE TO DISK;
RMAN> BACKUP TABLESPACE system;
72. How do you backup datafiles and control
files?
A:RMAN> BACKUP DATAFILE 3;
RMAN> BACKUP CURRENT CONTROLFILE;
Use a fast recovery without restoring all backups from their backup location to
the location specified inthe controlfile.
A:RMAN> SWITCH DATABASE TO COPY;
73. RMAN will adjust the control file so
that the data files point to the backup file location and then starts recovery.Why
use Rman ?
A. 1. No Extra Costs.. It is available free.
2.RMAN introduced in Oracle 8 it has become simpler with new version and
easier that user managed backups.
3.Proper Security
4.You are 100% sure your database has been backed up .
5.It contains details of backup taken in the central repository
6.Facility of Testing validity of backups also command like cross check
to checkthe status of backup.
7.Oracle 10g has got further optimized incremental backups with has
resulted inimprovement of performance during backup
8.and recovery time
9.Parrallel operation are supported
10.Better Querying facility for knowing different details of backup.
11.No Extra redo generated when backup is taken. compared to online
backup
12.Without rman.which results in saving of space in hard disk.
13.RMAN is an intelligent tool
14.Maintains repository of backup metadata.
15.Remembers backup locations
16.Knows what needs backup set locations
17.Knows what needs to be backed up
18.Knows what is required for recovery
19.Know what backups are redundant
20.It handles database corruptions
74. Oracle Enhancement for Rman in 10g
A. 1.Flash Recovery Area
2.Incrementally Updated Backups
3.Faster Incremental Backups
4.SWITCH DATABASE COMMAND.
5.Binary Compression
6.Global Scripting
7.Duration Clause
8.Configure This
9.Oracle Enhancement for Rman in 10g
10.Automatic Channel Failover
11.Compress Backup Sets
12.Recovery Through Reset Logs
13.Cross Backup Sets
75. Global Scripting
A.RMAN> print script full_backup to file 'my_script_file.txt'
Oracle Database 10g provides a new concept of global scripts, which you
can executeagainst any database registered in the recovery catalog, as long as
your RMAN client isconnected to the recovery catalog and a target database
simultaneously.CPISOLUTION.COM
RMAN> create global script global_full_backup
76. Outline
the steps for recovery of missing data file?
Losing Datafiles Whenever you are in NoArchivelog Mode:
###################################################
If you are in noarchivelog mode and you loss any datafile then whether it is
temporary or permanent media failure, the database will automatically shut
down. If failure is temporary then correct the underline hardware and start the
database. Usually crash recovery will perform recovery of the committed
transaction of the database from online redo log files. If you have permanent
media failure then restore a whole database from a good backup. How to restore
a database is as follows:
If a media failure damages datafiles in a NOARCHIVELOG database, then the only
option for recovery is usually to restore a consistent whole database backup.
As you are in noarchivelog mode so you have to understand that changes after
taken backup is lost.
If you logical backup that is export file you can import that also.
In order to recover database in noarchivelog mode you have to follow the
following procedure.
1)If the database is open shutdown it.
SQL>SHUTDOWN IMMEDIATE;
2)If possible, correct the media problem so that the backup database files can
be restored to their original locations.
3)Copy all of the backup control files, datafiles to the default location if
you corrected media failure. However you can restore to another location.
Remember that all of the files not only the damaged files.
4)Because online redo logs are not backed up, you cannot restore them with the
datafiles and control files. In order to allow the database to reset the online
redo logs, you must have to do incomplete recovery:
RECOVER DATABASE UNTIL CANCEL
CANCEL
5)Open the database in RESETLOGS mode:
ALTER DATABASE OPEN RESETLOGS;
In order to rename your control files or in case of media damage you can copy
it to another location and then by setting (if spfile)
STARTUP NOMOUNT
alter system set
control_files='+ORQ/orq1/controlfile/control01.ctl','+ORQ/orq1/controlfile/control02.ctl'
scope=spfile;
STARTUP FORCE MOUNT;
In order to rename data files or online redo log files first copy it to new
location and then point control file to new location by,
ALTER DATABASE RENAME FILE '+ORQ/orq1/datafile/system01.dbf';'
TO '+ORQ/orq1/datafile/system02.dbf';
Losing Datafiles Whenever you are in Archivelog Mode:
###################################################
If the datafile that is lost is under SYSTEM tablespace or if it is a datafile
contain active undo segments then database shuts down. If the failure is temporary
then correct the underline hardware and start the database. Usually crash
recovery will perform recovery of the committed transaction of the database
from online redo log files.
If the datafile that is lost in not under SYSTEM tablespace and not contain
active undo segments then the affected datafile is gone to offline. The
database remains open. In order to fix the problem take the affected tablespace
offline and then recover the tablespace.
77. Outline
the steps for recovery with missing online redo logs?
Redo
log is CURRENT (DB was shut down cleanly)
If the CURRENT redo log is lost and if the DB is closed consistently, OPEN
RESETLOGS can be issued
directly without any transaction loss. It is advisable to take a full backup of
DB immediately after the STARTUP.
Redo log is CURRENT (DB was not
shut down cleanly)
When a current redo log is lost, the transactions in the log file are also lost
before making to archived logs. Since a DB startup can no more perform a crash
recovery (since all the now-available online log files are not sufficient to
startup the DB in consistent state), an incomplete media recovery is the only
option. We will need to restore the DB from a previous backup and restore to
the point just before the lost redo log file. The DB will need to be opened in RESETLOGS mode. There is some transaction loss in this
scenario.
RMAN> RESTORE CONTROLFILE FROM '<backup tag
location>';
RMAN> ALTER DATABASE
MOUNT;
RMAN> RESTORE DATABASE;
RMAN> RECOVER DATABASE
UNTIL TIME "to_date('MAR 05 2009 19:00:00','MON DD YYYY
HH24:MI:SS')";
RMAN> ALTER DATABASE
OPEN RESETLOGS;
78. Outline
steps for recovery with missing archived redo logs?
If a redo log file is already archived, its loss
can safely be ignored. Since all the changes in the DB are now archived and the
online log file is only waiting for its turn to be re-written by LGWR (redo log
files are written circularly) the loss of the redo log file doesnt matter much.
It may be re-created using the command
SQL> STARTUP MOUNT;
SQL> ALTER DATABASE CLEAR
LOGFILE GROUP <group#>;
This will re-create all groups and no transactions are lost. The database can
be opened normally after this.
79. What
is FRA ? When do you use this ?
Flash recovery area where you can store not
only the traditional components found in
a backup strategy such as control files, archived log files, and Recovery
Manager (RMAN) datafile copies but also a number of other file
components such as flashback logs. The flash recovery area simplifies backup
operations, and it increases the availability of the database because many
backup and recovery operations using the flash recovery area can be performed
when the database is open and available to users.
Because the space in the flash recovery area
is limited by the initialization parameter DB_ RECOVERY_FILE_DEST_SIZE , the
Oracle database keeps track of which files are no longer needed on disk so that
they can be deleted when there is not enough free space for new files. Each
time a file is deleted from the flash recovery area, a message is written to
the alert log.
A message is written to the alert log in other
circumstances. If no files can be deleted, and the recovery area used space is
at 85 percent, a warning message is issued. When the space used is at 97
percent, a critical warning is
issued. These warnings are recorded in the alert log file, are viewable in the
data dictionary view DBA_OUTSTANDING_ALERTS , and are available to you on the
main page of the EM Database Control
80. What
is Channel? How do you enable the parallel backups with RMAN?
Channel is a link that RMAN requires to link
to target database. This link is required when backup and recovery operations
are performed and recorded. This channel can be allocated manually or can be
preconfigured by using
automatic channel allocation.
The number of allocated channels determines
the maximum degree of parallelism that is used during backup, restore or
recovery. For example, if you allocate 4 channels for a backup operation, 4
background processes for the operation can run concurrently.
Parallelization of backup sets allocates
multiple channels and assigns files to specific channels. You can configure
parallel backups by setting a PARALLELISM option of the CONFIGURE command to a
value greater than 1 or by
manually allocating multiple channels.
RMAN> CONFIGURE DEVICE TYPE PARALLELISM 2
BACKUP TYPE TO COMPRESSED BACKUPSET;
81. What
are RTO, MTBF, and MTTR?
RTO: Recovery Time objective-is the maximum
amount of time that the database can be unavailable and still stasfy SLA's
MTBF (Meant tiem Between Failure)-
MTTR (Mean tie to recover)- fast recovery solutions
82. How
do you enable the encryption for RMAN backups?
If you wish to modify your existing backup
environment so that all RMAN backups are encrypted, perform the following
steps:
· Set up the Oracle Encryption Wallet
· Issue the following RMAN command:
RMAN> CONFIGURE ENCRYPTION ALGORITHM
'AES256'; -- use 256 bit encryption
RMAN> CONFIGURE ENCRYPTION FOR DATABASE ON; -- encrypt backups
83. What
is the difference between restoring and recovering?
Restoring involves copying backup files from
secondary storage (backup media) to disk. This can be done to replace damaged
files or to copy/move a database to a new location.
Recovery is the process of applying redo logs
to the database to roll it forward. One can roll-forward until a specific
point-in-time (before the disaster occurred), or roll-forward until the last
transaction recorded in the log files.
SQL> connect SYS as SYSDBA
SQL> RECOVER DATABASE UNTIL TIME '2001-03-06:16:00:00'
USING BACKUP CONTROLFILE;
RMAN> run {
set
until time to_date('04-Aug-2004 00:00:00', 'DD-MON-YYYY HH24:MI:SS');
restore database;
recover database;
}
What
are the various tape backup solutions available in the market?
How
do you generate the begin backup script?
Outline
the steps for recovering the full database from cold backup?
Explain
the steps to perform the point in time recovery with a backup which is taken
before the resetlogs of the db?
Outline
the steps involved in TIME based recovery from the full database from hot backup?
Is
it possible to take Catalog Database Backup using RMAN? If Yes, How?
Can
a schema be restored in oracle 9i RMAN when the schema having numerous table
spaces?
Outline
the steps for changing the DBID in a cloned environment?
How
do you identify the expired, active, obsolete backups? Which RMAN command you
use?
Explain
how to setup the physical stand by database with RMAN?
List
the steps required to enable the RMAN backup for a target database?
How
do you verify the integrity of the image copy in RMAN environment?
Outline
the steps involved in SCN based recovery from the full database from hot backup?
Outline
the steps involved in CANCEL based recovery from the full database from hot
backup?
Outline
the steps involved in TIME based recovery from the full database from hot backup?
Is
it possible to specific tables when using RMAN DUPLICATE feature? If yes, how?
Explain
the steps to perform the point in time recovery with a backup which is taken
before the resetlogs of the db?
Outline
the steps for recovering the full database from cold backup?
How
do you generate the begin backup script?
