Zero Downtime Backup of MaxDB database with HP Data Protector

Appendix H

This is a reproduction of SAP Note 616814 downloaded on 28 July, 2008.

Note 616814 - Suspend log writer for split mirror or snapshot

Note Language: English Version: 13 Validity: Valid from 08.11.2006

Summary

Symptom

You want use a split mirror or snapshot of the storage system for data

backups with MaxDB or liveCache. The storage system cannot ensure the

consistency of the I/O for all data volumes, in other words the storage

system cannot create a point-in-time image.

More Terms

EMC, Symmetrix, ESS, XP512, Network Appliance, Filer, StorageWorks,

StorEdge, backup, consistent, instance, spli,t BCV, flashcopy, DPM

Cause and Prerequisites

SAP DB, MaxDB or liveCache version

7.3.0 Build 44 or higher (SAP DB only)

7.4.2 Build 18 or higher

7.4.2 Build 21 or higher

7.5.0

All higher versions

Additional information:

As of SAP DB Version 7.3.0 Build 35, you can stop the log writer, however,

this results in incorrect displays. Therefore, we recommend that you only

use these functions as of 7.3.0 Build 44 or higher.

Solution

SAP DB provides the option of using split mirrors or snapshots for data

backups even if the disk system used cannot guarantee the I/O consistency

of all data volumes of a database instance.

The log writer can be suspended for this purpose in SAP DB. In this way,

you ensure that no more Savepoints (or Checkpoints in 7.3) can be written.

The relevant last created savepoint serves as an entry point for a

restart or a recovery. Changes to data between two Savepoints are not

written back to the old block position.

If the log writer is suspended, the last Savepoint is already stored on

the data disks. A new Savepoint can only be created when the log writer

is activated again.

If a split or snapshot is created in the time of the suspended log writer,

the corresponding disk image contains a complete savepoint on which the

database can be based during a restart or restore.