Ensuring DBUTLTY quality of BACKUP or EXTRACT while database is open

Products

• Datacom/DB
• Datacom
• Datacom/AD

Issue/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.

This article will discuss how to have a current, stable, steady-state data backup, whether using DBUTLTY Physical BACKUP or EXTRACT, or using non-DBUTLTY tools like ADRDSSU (DFDSS).

Environment

 

 

Resolution

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

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

• Using a DBUTLTY SEQ=PHYSICAL backup will automatically flush the pipeline at the start of the backup function.
• Use the DBUTLTY COMM CLOSE function to close individual areas or all areas in one or more databases. When the CLOSE function has completed successfully, all data in buffers 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 of a database while the Multi-User Facility is active.
  

  Note that 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 available.
• 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. 

 

Additional Information

For more information about the DBUTLTY functions COMM CLOSE, ACCESS, BACKUP, and EXTRACT, please refer to the DBUTLTY Reference documentation.

For more information about the COMM QUIESCE processing, please refer to the Datacom/DB Database and System Administration documentation.

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