Recovery points

If you use either full-function or Fast Path DEDB databases, you can create recovery points in the database without having to take IMS offline. By creating recovery points you will improve the recovery of the database when an outage occurs.

When you quiesce the database you establish a point of consistency, which is when there are no updates pending for the database and the information stored on a direct access storage device (DASD) accurately reflects the current information stored in the database. When this point of consistency is reached, you create an image copy that you can use to provide a quick method of recovering the database to this point.

Important: This process must occur on every IMS in an IMSplex that is actively using the database.

You can create this point of consistency without making the database unavailable to applications. When the quiesce command is invoked, all updates that are in progress are committed and stored on DASD. However, the next DL/I call that attempts to access the database results in a wait until the quiesce on the database is released. Once the quiesce is released, these applications can access the database again.

There are two ways to quiesce the database using the UPDATE DB command with the START(QUIESCE) keyword:

START(QUIESCE): This command causes the database to become quiesced and then releases the quiesce, thereby creating the new recovery point for the database. This is the default form of the quiesce command.

START(QUIESCE) OPTION(HOLD): This command causes the database to become quiesced and keeps the database quiesced until an UPDATE DB STOP(QUIESCE) command is issued that releases the quiesce. While the database is quiesced, you can create image copies of the database data sets.