A backup is a copy of one or more dbspaces (also called storage spaces) and logical logs that the database server maintains. On Dynamic Server, you can also back up blobspaces and sbspaces. On Extended Parallel Server, you can also back up dbslices. For a description of storage spaces, see your IBM Informix: Administrator's Guide.
The backup copy is usually written to a secondary storage medium such as disk, magnetic tape, or optical disk. We recommend that you store the media offline and keep a copy off-site if possible.
Figure 1 illustrates the basic concept of a database backup.
You do not always have to back up all the storage spaces. If some tables change daily but others rarely change, it is inefficient to back up the storage spaces that contain the unchanged tables every time that you back up the database server. You need to plan your backup schedule carefully to avoid long delays for backing up or restoring data.
To provide a more flexible backup environment, ON–Bar and ontape support the following three backup levels:
You need all these pages to restore the database to the state that it was in at the time that you made the backup.
All changed table and index pages are backed up, including those with deleted data. The data that is copied to the backup reflects the state of the changed data at the time that the level-1 backup began.
A level-2 backup contains a copy of every table and index page in a storage space that has changed since the last level-1 backup.
For details, see Backing Up with ON-Bar, and Backing Up with ontape.
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