You must always have a recent and consistent copy of database data that can be used to recover the database in the event of failure involving data loss. Informix provides the following tools for database recovery (including backup):
· ON-Bar (the most recent tool) together with a storage manager such as the Informix Storage Manager (ISM)
For an introduction to backup with Informix, see the following:
When ON-Bar was released, Informix changed the terminology to bring it into line with other databases. The term "archive" from ON-Archive and ontape is no longer used with ON-Bar. Instead, "database backup" is used.
In this section, we:
· Use "database backup" to include the term "archive."
· Concentrate on ON-Bar, giving cross-references only to ON-Bar sections in the documentation for Informix issued by SAP.
1. You develop a robust and secure backup strategy. Refer to:
Consider factors such as the frequency of backups, the level of database backups, whether you want to use the Database Planning Calendar of the Computing Center Management System (CCMS) to schedule backups, whether you want to perform manual or continuous backups, how long you intend to keep the storage media with the backups before they are overwritten, whether you want to use unattended backups, and so on.
SAP recommends you to:
· Use full (level-0) database backups as often as possible, preferably once per day. Remember that you cannot use incremental (that is, level-1 or level-2) database backups independently of the corresponding level-0 backup. Full (level-0) archives are also required in special circumstances, for example, if you alter the configuration of the Informix server.
· Avoid partial backups. This is because they are not independent in two ways. First, they require a backup of the logical log data from the time when the archive was taken. Second, from the recovery point of view, it makes little sense to only restore part of the database because the SAP System is so integrated.
2. If necessary, you consider parallel database backup (known as a "dbspace backup" with ON-Bar) to speed up the backup. This can help you to avoid affecting the performance of your production system during working hours. ON-Bar and all storage managers fully support parallel backup. Informix allows you to create backups while the system is fully online and no extra risk is incurred.
3. Before you create a database backup, you check physical database consistency. Be sure to always have at least one database backup for which you have checked the consistency. If a backup is inconsistent, you might be unable to use it to restore the database.
4. You check and review your backup strategy. For example, this might include testing that you can use the backups to successfully restore the database from time to time, using a copy of the production system on a separate machine.
SAP recommends you to pay special attention to logical-log backup, because this often causes problems. If the logical log fills, the database stops processing, so stopping production with your SAP system. For more information, see Preventing Emergency Logical-Log Backup.
You always have an up-to-date backup of your database. This allows you to quickly recover the database in the event of a failure involving data loss. Therefore, the availability of your SAP system is increased because downtime due to the absence of a suitable database backup is kept to a minimum.