When you perform a restore operation, DB2® database products will automatically
choose an optimal value for the number of buffers, the buffersize
and the parallelism settings. The values will be based on the amount
of utility heap memory available, the number of processors available
and the database configuration.
Therefore, depending on
the amount of storage available on your system, you should consider
allocating more memory by increasing the
util_heap_sz configuration
parameter. The objective is to minimize the time it takes to complete
a restore operation. Unless you explicitly enter a value for the following
RESTORE
DATABASE command parameters, DB2 database
products will select one for them:
- WITH num-buffers BUFFERS
- PARALLELISM n
- BUFFER buffer-size
For restore operations, a multiple of the buffer size used by
the backup operation will always be used. You can specify a buffer
size when you issue the
RESTORE DATABASE command
but you need to make sure that it is a multiple of the backup buffer
size.
You can also choose to do any of the following to reduce the amount
of time required to complete a restore operation:
- Increase the restore buffer size.
The restore buffer size
must be a positive integer multiple of the backup buffer size specified
during the backup operation. If an incorrect buffer size is specified,
the buffers allocated will be the smallest acceptable size.
- Increase the number of buffers.
The
value you specify must be a multiple of the buffersize that was used
for the backup, otherwise it will be rounded down to the closest multiple
of the backup buffersize.
- Increase the value of the PARALLELISM parameter.
This will increase the number of buffer manipulators (BM) that
will be used to write to the database during the restore operation.
- Increase the utility heap size
This will increase the memory
that can be used simultaneously by the other utilities.
DB2 10.5 for Linux, UNIX, and Windows