Recovery with MaxDB
Purpose
To minimize
downtime with your MaxDB database instance, you must make sure that you can
quickly restore the database instance in the event of a system failure in
which productive data is lost. A database instance can only be recovered in
ADMIN
operational state
using the
Database
Manager.
Prerequisites
When recovering data you must restore (the sequence is important):
...
1.
The last complete
data
backup in either ONLINE or ADMIN state. This step is mandatory.
2. Subsequent incremental data backup, if available.
3.
Any required
log backups.
The Database Manager prompts you for the correct sequence of log
backups.
Process Flow
...
1. You design a recovery strategy and test it.
Think in advance what must be done if the database instance suddenly fails and the data must be restored. Plan the steps carefully and rehearse the procedure using a test system, if possible. This substantially reduces downtime.
2. You use the recovery report in the SAP system.
You can
obtain a list of the data backups (complete and incremental) and log backups
required for a recovery by using the
DBA History in the
SAP system. Print this report regularly, so that you have an up-to-date list
of the required backups, if a recovery is later necessary.
3. You always have the best possible set of data available.
This means that the users need not spend extra time on manually restoring lost data, if a recovery is necessary.
4. You make sure that you can quickly identify the tapes required.
To recover the database instance, you must know exactly which types of backup media you need (that is, complete data backup, incremental data backup, or log backup media). A data backup (including incremental data backups) can consist of several backup media. You do not have to start restoring data with the first backup nor do you have to finish with the last one. As long as the media belong to the same backup (complete or incremental, parallel or not) the sequence of the media is not important. You can use the Database Manager to display the media information.
However, you must restore the individual data backups in the correct sequence. To restore the log entries, you must restore the backup media in the correct sequence (that is, in the sequence in which the log backups were performed).
5. You choose the fastest recovery strategy.
Start with the recovery of data backups. It is normally faster to restore incremental backups than to restore the log backup. To reduce the time taken still further, consider using parallel recovery, that is, with several backup devices working simultaneously in parallel. If you are using incremental backups as well as log backups, you must use the incremental backups first, followed by the log backups.
When recovering a database instance, you normally need to restore log backups too. Sometimes the relevant log entries are still in the log area (that is, they have not yet been backed up). In this case the log recovery does not take place explicitly. The relevant log entries are restored when the database instance is restarted. If there are log entries required for recovery but these are no longer in the log area, the system guides you accordingly.
See also:
Concepts of the Database System,
· Administration