Database Backups

Backing up Databases with TSM

Database backups are usually a bit special as a database usually consists of a number of physical files that all need to be backed up as an entity, often with consistent time stamps. Databases also have transaction logs to ensure that the data stored in a database is consistent, even after a hardware failure. Databases usually have internal catalogs which record these files, so when you do a restore, you need to make sure that the catalogs hold the correct information too. To help with this lot, databases have a Database Management System (DBMS), which tracks physical database files, transaction logs and backups. A DBMS will usually be able to run a backup while the database is active, which effectively means no backup window is required.

If you are using TSM, you have three options available to get a good backup of a database

  1. Stop the database and backup it up with the standard TSM client. You will get a good, consistent backup but this means application downtime.
  2. Using the DBMS backup utility, back the database up to a file on disk, then back that file up to tape using the standard TSM client. This will need extra disk space, and a way to resolve the scheduling issues between database backup and TSM backup to ensure that the TSM backup does not start until the database backup completes successfully.
  3. Back the database up with the TSM Tivoli Data Protection module. This is the best method because it is simple, allows you to backup the databases with the database active, and interfaces with the DBMS utilities

TDPs exist for Oracle, Informix and MS-SQL databases; and also Lotus Domino and MS-Exchange e-mail databases. DB2/UDB does not have a TDP but uses the TSM API to get a consistent database backup.

Third Party products

There is a third party product called Repostor that you can use to interface with a number of other databases, including FirebirdSQL, Ingres, MariaDB, MySQL, PostgreSQL, Progress, Sybase ASE and Sybase IQ. MySQL is especially popular as it is the database component of WAMP and LAMP internet servers. Repostor runs on most popular platforms: AIX, HP-UX, Linux (Redhat AND SLES) and Windows.

Repostor comes in two flavours, Snap Protector and Data Protector. As you might expect, Data Protector backs up from the database itself while Snap Protector backs up from a snapshot.

Data Protector integrates between the specific DBMS and TSM to provide a secure database backup. Exactly what it can do depends on the DBMS so you need to check out the Repostor website for specific information. In general you get the normal TSM backup and restore facilities like full and incremental backups, full, incremental and point in time restores, including restore from older backup, restore to new name and restore to new machine. You also get comprehensive reporting facilities, not just on backup versions but also used backup capacity and compression and deduplication savings.

As well as backups from snapshots, Snap Protector lets you quickly roll a database back to any point in time from snapshot plus block changes on the TSM Server and lets you recover to any point in time using backed up transaction logs. After the initial snapshot, only block changes are sent to the TSM Server and after a snapshot restore, only changed blocks will be restored from the TSM Server.

Protector is licensed by each backed up host and it is possible to download a free 30 day evaluation copy - see the Repostor website for details.

It is also possible to interface TSM with DBMS systems for other databases using ADSMPIPE. This is described in the red paper

http://www.redbooks.ibm.com/abstracts/redp3980.html

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