Informix Archive (SAP Library - SAP Database Guide: Informix (BC-DB-INF-DBA))

Informix Archive

Use

An archive is a copy taken with ON-Archive or ontape of all or a portion of the data that the Informix database server manages.

To be exact, an archive is a copy of one or more dbspaces with any extra system information required to regenerate the data exactly as it was when copied. The purpose of an archive is to enable database data to be recovered or restored to a consistent state after a failure in which data is lost or damaged. Archives are normally written to tape, although archives to disk are also possible.

Integration

Informix supplies tools that you can use to perform an archive. See Comparison of ontape, ON-Archive, and ON-Bar for Data Recovery for a comparison of these tools.

Features

There are the following types of archives:

Sequential

This is the usual type of archive where data is written to a single storage device. A sequential archive is entirely self-sufficient and can be used to restore database data without any additional information.

Parallel

If you wish to increase the speed of the archive (for example, if you have a large system with a great deal of data), you can use this type of archive. Data is written simultaneously in parallel from several dbspaces to a series of storage devices. A parallel archive is not self-sufficient – you must create logical-log backups for the period of the archive in order to be able to restore the database later.

The following graphic shows the main features of sequential and parallel archives:

Sequential and Parallel Archives

This graphic is explained in the accompanying text

Activities

You can archive at different levels:

Level-0. The entire database (that is, all dbspaces) is archived. This is the safest archive because it is self-sufficient to restore the data. However, it might take a long time to complete if your database is large.

Incremental. There are the following types of incremental archive:

Level-1

This archives only data that has changed since the last level-0 archive.

Level-2

This archives only data that has changed since the last level-1 archive.

The following diagram illustrates this concept:

Archive Levels

This graphic is explained in the accompanying text

The scope of the archive refers to what portion of the database is included. With ON-Archive , it is possible to archive only a subset of the data by using dbspace sets. However, we recommend you to always perform full-system archives, that is, to archive the entire database – whether at level-0, level-1 or level-2.

You can use the DBA Planning Calendar in the Computing Center Management System (CCMS) of the SAP System to schedule archives, but not if you are using ontape as your archive tool. The DBA Planning Calendar also enables you to look at the results of past archives and see the resources that are required for future archives.

Archive data is written to a save set on the storage medium.

See also: