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User Guide
OpenEdge Replication Quick Command Summary : Backing up an online target database
 

Backing up an online target database

You can perform an online backup of the target database outside of transition while OpenEdge Replication is running. The OpenEdge Replication agent is the only process that can update the target database; in the case of the online backup, however, no changes to the database itself occur. The backup process locks buffers and blocks but not database records.
Note: The Replication agent must be in a "normal processing" state for the online backup to execute. Verify that your agent is in a "normal processing state using one of the following:
*Query the _ReplAgent VST. See Virtual system tables for OpenEdge Replication.
*Query the agent status with DSRUTIL STATUS. See DSRUTIL status qualifier.
*Check the agent status with DSRUTIL MONITOR. See DSRUTIL monitor qualifier.
When an online backup of the target database is underway, activity continues on the source database as long as:
*Asynchronous replication is being performed.
*The Replication server is able to acquire a shared schema lock on the source database. The server must acquire the schema lock to block updates to the source database schema during the synchronization process.
Source database activity continues while the online backup is being performed on the target database, as long as there is enough available AI extent space.

To begin

You begin the online backup process by using the PROBKUP command:
probkup online db-name [incremental] device-name [parameters]

Where:

online
Indicates the backup is taking place online.
db-name
Specifies the database you want to back up.
incremental
Indicates that the backup is an incremental backup.
device-name
Identifies a special device (for example, a tape drive) or a standard file. If device-name identifies a special device, PROBKUP assumes the device has removable media, such as a portable hard drive or a USB memory stick. For Windows, use \\.\tape0 for the device name if you are backing up to a tape drive.
parameters
Indicates any additional parameters you want to use with PROBKUP.
For more general details about database backup, see OpenEdge Data Management: Database Administration.

What happens during an online backup of the target database

For the online backup of the target database to be successful, coordination between the backup process and OpenEdge Replication is necessary. The following is a summary of how the backup process and OpenEdge Replication work together to ensure that the backup proceeds properly once you enter the PROBKUP command:
1. If the Replication agent is active:
a. The online backup utility sends a message to the Replication agent indicating that an online backup is about to begin.
b. The Replication agent informs the Replication server that an online backup of the target database is about to start, provided that:
*The target database is not currently blocked (due to a quiet point, a BI stall, an AI stall, or another online backup).
*The Replication agent is connected to the Replication server.
*Synchronization is not currently being performed.
2. One of the following actions then occurs:
*If the Replication server can acquire a shared schema lock on the source database and asynchronous replication is being performed, the Replication server will indicate to the database that it is busy. This allows activity on the source database to continue.
*The Replication server then sends a positive response to the Replication agent, and activity continues as described in the next step.
*If the Replication server cannot acquire the shared schema lock, the server notifies the Replication agent, and the Replication agent then notifies the user who started the backup that the backup cannot be performed at this time.
3. If the Replication agent receives a positive response from the Replication server (as described in the previous step), the online backup is allowed to continue.
4. The online backup utility then performs the online backup of the target database.
5. When the backup finishes, a completion message is sent to the Replication agent.
6. The Replication agent then sends a completion message to the Replication server.
7. The Replication server enters recovery and begins synchronization, which updates the target database with all activity that occurred on the source database while the online backup was running on the target.
Once recovery synchronization completes, the Replication server returns to normal processing.
8. Online backup completes processing.