Backing up a database in a partitioned
database environment can pose difficulties such as tracking the success
of the backup of each database partition, managing the multiple log
files and backup images, and ensuring the log files and backup images
for all the database partitions span the minimum recovery time that
is required to restore the database.
Using a single system
view (SSV) backup is the easiest way to back up a partitioned database.
About this task
There are four ways to back up a database in a partitioned
database environment:
- Back up each database partition one at a time by using the BACKUP
DATABASE command, the BACKUP DATABASE command
with the ADMIN_CMD procedure, or the db2Backup API.
- Use the db2_all command
with the BACKUP DATABASE command to first back
up the catalog partition and then to back up a specified list of database
partitions.
- Run a single system
view (SSV) backup to back up some or all of the database partitions
simultaneously, including the catalog partition.
- Use a task assistant in IBM® Data
Studio to
guide you through the process of backing up the database.
Backing up each database partition one at a time is time-consuming
and error-prone. Backing up all the partitions by using the db2_all command
is easier than backing up each database partition individually because
you generally only must make one command call. However, when you
use db2_all to back up a partitioned database,
you sometimes still must make multiple calls to db2_all because
the database partition that contains the catalog cannot be backed
up simultaneously with non-catalog database partitions. Whether you
back up each database partition one at a time or use db2_all,
managing backup images that were created using either of these methods
is difficult because the time stamp for each database partition's
backup image is different, and coordinating the minimum recovery time
across the database partitions' backup images is difficult as well.
For the previously mentioned
reasons, the recommended way to back up a database in a partitioned
database environment is to use an SSV backup because you can decide
to back up all database partitions simultaneously, including the catalog
partition, and get the same time stamp for each database partition backup. Alternatively,
you can split your backup, specifying some database partitions for
which you get the same time stamp, and later take additional backups
on the other database partitions to complete the database backup.
The catalog partition can be backed up at any time with any other
database partitions.
Note: For restore operations, you still must restore
the catalog partition before you restore some or all of the other
database partitions.
Procedure
To back up some or all of the database partitions of
a partitioned database simultaneously by using an SSV backup:
- Optional: Allow the database to remain online,
or take the database offline.
You can back up a partitioned
database while the database is online or offline. If the database
is online, the backup utility acquires shared connections to the other
database partitions, so user applications are able to connect to database
partitions while they are being backed up.
- On the database partition that contains the database catalog, perform the backup with
appropriate parameters for partitioned databases, using one of the following methods:
- Run the BACKUP DATABASE command with the ON
DBPARTITIONNUMS parameter.
- Run the BACKUP DATABASE command with the ON
DBPARTITIONNUMS parameter by using the ADMIN_CMD procedure.
- Call the db2Backup API with the iAllNodeFlag
parameter.
- Open the task assistant for the BACKUP DATABASE command in IBM Data
Studio.
For
example, to backup the sample database in a DPF environment perform the following
command:
db2 backup database sample on all dbpartitionnums to /db2home/db2inst1/backup/ without prompting
- Optional: Include the log files that are required
for recovery with the backup images.
By default, log
files are included with backup images if you are performing an SSV
backup (that is, if you specify the ON DBPARTITIONNUM parameter).
If you do not want log files to be included with the backup images,
use the EXCLUDE LOGS command parameter when you
run the backup. Log files are excluded from the backup image by default
for non-SSV backups.
For more information, see Including log files with a backup image.
- Optional:
Delete previous backup images.
The method that you use to delete old backup images depends on how you store the backup
images. For example, if you store the backup images to disk, you can delete the files; if you store
the backup images using IBM
Tivoli® Storage Manager, you can use the
db2adutl utility to delete the backup images. If you are using Db2® Advanced Copy
Services (ACS), you can use the db2acsutil command to delete snapshot backup
objects.