Backup and Recovery:
Logging:
When you make a backup plan, you should
consider using the database logging mode. The database records every change of
rows in tables, and each database object. These logs or log files are used to
recover from applications from system errors.
1. Circular
logging
2. Archive
logging3. Dual logging
Circular logging:
By default, the logs are written in a circular
fashion. The first log is overwritten once the cycle is completed. In this
manner, the data in the logs files are always overwritten. So there is data loss.
With circular logging, you can only
do offline database backup. Users cannot use the database while an offline back
up is taking place.
This backup is only used for the
version recovery, that is recovering a database to the last backup time. Log
files are not applicable for version recovery.
Archive logging:
Here the primary logs in the memory
(RAM) are written first. Once the transaction is committed, the data is written
to the disk. Once all the primary logs are filled, the data in the first log is
transferred to the secondary logs in the disk & it is cleared to hold the
coming transactions data. In this manner there is no data loss as the log files
are not overwritten anywhere.
The archive mode supports online
backup and database recovery using log files called rollforward recovery.
The logging mode can be changed from
circular to archive by setting parameters LOGRETAIN or USEREXIT to ON.
Set
either of these 2 parameters.
db2
UPDATE DB CFG FOR <dbname> USING LOGRETAIN RECOVERY/ON
db2 UPDATE DB CFG FOR <dbname> USING
USEREXIT ON
You
can also do a Table space either offline or online.
1.
Active logs files.
2.
Archive log files.
-
Full backup.
- Incremental Backup and Recovery.
- Delta backup and recovery.
Syntax: BACKUPDATABASE <db Name> [USER <User_Name> USING <pwd>]
[TABLESPACE
( TableSpaceName) ] [ONLINE]
[INCREMENTAL / DELTA]
TO
<Location>
[WITH
<Num_of_ Buffers> BUFFERS] [BUFFER <Buffer Size> K]
[PARALLELISM <Parallelism_Num> ]
[WITHOU
Create New TablespaceT PROMPTING]
[COMPRESS]
Ex:
- ]$ db2 backup database
cartdb online to /home/itlokam with 2 buffers buffer 1024 parallelism 2 without
prompting
Duel Logging:
To
prevent the log failures, which could be caused by administrators, who
accidentally delete corrupted active logs or log files at the hardware level.
Dual logging can be enable by setting the
DB2 registry Variable : DB2_NEWLOGPATH2 to 1.
If an error happens and a message
will be written to the db2diag.log.
$db2set DB2_NEWLOGPATH=1
configuration of the second log path is controlled by the database configuration parameter mirrorlogpath. When a value is present in mirrorlogpath dual logging is enabled.
db2 update db cfg for <dbname> using MIRRORLOGPATH <LOG_DIR2>
Afterwards you must have to restart the instance through db2stop force and db2start.
configuration of the second log path is controlled by the database configuration parameter mirrorlogpath. When a value is present in mirrorlogpath dual logging is enabled.
db2 update db cfg for <dbname> using MIRRORLOGPATH <LOG_DIR2>
Afterwards you must have to restart the instance through db2stop force and db2start.
What is meant by Dual Logging ?
ReplyDeleteIf you enable the Duel logging to the database you need to change these parameters
ReplyDeletedb2 registry variable DB2_NEWLOGPATH2 set to value 1
update dbcfg parameter mirrorlogpath
db2 update db cfg for using MIRRORLOGPATH
hi this is kishore ....
ReplyDeletedb2 UPDATE DB CFG FOR USING USEREXIT ON use this command where the log files are store ...