There are three models for backing up applications:

• The application maintains a transaction log for each transactional unit of work. A backup can be taken any time the application is running. If the data is recovered, the transaction log can be used to either back out, or redo, the transactions to reach a known sync point for the application.
• The application provides a quiesce capability, during which time transactional updates are suspended.
• The application does not provide either a transaction log or quiesce capability. In this simplest case, it is suggested that the backups occur only when the files are closed. If backups are taken while the files are open, it might be difficult to determine which transactions were fully recorded, and which others were still in flight.

IBM® offers three ways to perform backups and maintain an inventory of their attributes:

• DFSMShsm
• Tivoli® Storage Manager, formerly known as ADSTAR Distributed Storage Manager (ADSM)
• DFSMSdss