Backup Engine Concepts

This section describes the concepts related to backup and restore, such as backup and restore types, and data owners.

Backup and Restore

Backup works by copying files (installed applications, Secure ID and data) from a Symbian device to a PC.

Restore works by copying previously backed up files from the PC to the Symbian device.

The Symbian platform allows different ways to differentiate backup and restore:

  • Based or Incremental

    Base backup/restore is a backup (or restore) that includes all the selected files in all or part of a drive.

    Incremental backup/restore includes only files that are new or changed since a previous backup (or restore). An incremental backup is normally smaller than a base backup and will take less time.

  • Full or Partial

    In a full backup/restore operation, all the data is selected for backup (or restore).

    In a partial backup/restore operation, the data of only a specific list of data owners are selected for backup (or restore).

  • Passive, active or proxy

    According to the type of a data owner, backup/restore can be passive, active or proxy. For more information, refer to Data Owner.

Data Owner

In the Symbian platform, private data, CentRep repositories and DBMS databases are owned directly or indirectly by a Symbian process. Each Symbian process can be identified by its Secure ID (SID - a 32-bit number) and can have its own private directory identified by its SID. Directories and files under this private directory are owned by the process.

Data owners on the device can opt to have their data backed up in the following ways:

  • Passive: Simply copies disk files belonging to the data owner. The backup registration file is used to list the files and/or directories to backup and restore.

  • Active: The data owner is called upon to supply the data directly to the Backup Engine at backup time (causing the process to be started if it is not already running). Similarly, the data is supplied back to the process on restore.

  • Active Proxy: If the data owner has data stored by another service on the device (e.g. central repository) then this service can be called upon to backup and restore this data on behalf of the data owner. The service is referred to as an active proxy, and behaves in a similar way to an active data owner.