How can I be sure that a DBUTLTY physical sequence BACKUP or EXTRACT has all current data without shutting down the Multi-User Facility (MUF)?

Document ID : KB000024005
Last Modified Date : 14/02/2018
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Introduction:

Using DBUTLTY to perform a physical sequence BACKUP or EXTRACT of data allows the function to process without taking the database out of operation, but because it works with the copy of the database on disk, there is a challenge in making sure the data is current and complete.

Instructions: 

To improve data handling efficiency, a CA Datacom MUF will often have some or all of the records in a database table in its memory. Since a physical sequence BACKUP or EXTRACT deals exclusively with the data as it exists on the disk device, the records on the device may not always match what is in memory.

Without shutting down the MUF, here are some options for ensuring the data in memory is written to the disk device.

  • Use the DBUTLTY COMM CLOSE function to close individual areas in a database or all areas in one or more databases. When the CLOSE function has completed successfully, all data in memory will have been written to the disk device. This command is often used in conjunction with the DBUTLTY ACCESS function to control access to a database while the backup process takes place. The ACCESS function provides the ability to allow or disallow an open of a User Requirements Table specified at the database level while the Multi-User facility is active. You can also use it to allow or disallow the ability of applications to execute maintenance to a database while Multi-User Facility is active.

    If turning off access to a database using the DBUTLTY ACCESS function, following the BACKUP or EXTRACT processing, it will be necessary to execute another DBUTLTY ACCESS function to allow access to the database again.
  • Use the COMM OPTION=STATS function. This will flush all statistics for the specified database, or for all databases if no DBID= value is provided, and it will also flush any pipeline updates to disk. This allows all access to continue as normal, and will allow the data on disk to be more current, although any updates since the COMM OPTION=STATS function will not be there.
  • Use the COMM QUIESCE console command. This command provides a way to quiesce or pause record maintenance activity in the MUF. The request can be made at a transaction boundary, where syncpoints and rollbacks can be completed, or it can be made at an individual MUF request boundary. Once the COMM QUIESCE is successfully in effect, all data in memory will have been written to the disk device.

    Following the BACKUP or EXTRACT processing, it will be necessary to allow record maintenance activity to continue by issuing a COMM QUIESCE OFF console command.

    Note that the COMM QUIESCE command affects all databases and record maintenance activity in the MUF, and cannot be restricted to a single database or area.

Additional Information:

For more information about the DBUTLTY functions COMM CLOSE, ACCESS, BACKUP and EXTRACT, please refer to the following Guides:

CA Datacom/DB Version 14.02 DBUTLTY Reference Guide

CA Datacom/DB Version 15.0 DBUTLTY Reference Guide

For more information about the COMM QUIESCE processing, please refer to the following Guides:

CA Datacom/DB Version 14.02 Database and System Administration Guide

CA Datacom/DB Version 15.0 Database and System Administration Guide

As always, please contact CA Technologies support for CA Datacom if you have further questions.

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