Storing transaction logs in a database for high availability

You can configure transaction logs to be stored in a database where you can implement automatic replication and simpler disaster recovery.

Before you begin

For more information about this feature and why it can be useful, read Runtime logs in a database: Overview. Configure the transaction log location and the compensation log location for each server in the cluster before you enable high availability.

About this task

This solution uses two data centers. One is the primary data center and the other is a standby data center. The installation and configuration data from the primary data center is copied to the standby data center. Database replication is used to synchronize replication of runtime data from the primary database to the standby database.

Procedure

At the primary site, install BPM on all nodes and create a deployment environment as you would normally.
Set up and configure the database.
1. Install the database for the primary data center.
2. Use generated database scripts to create database objects.
3. Install the database in corresponding standby data center.
4. Configure the databases to implement data replication between the primary database and the standby database.
Configure the transaction service.
1. Start the deployment environment at the primary data center.
2. For each cluster member in the application cluster and in the support cluster, create a data source on the cluster level. Configure the logs for the transaction service and the compensation service for each cluster member into the database. Use a unique prefix for each member. See detailed instructions in Storing transaction and compensation logs in a relational database for high availability in the WebSphere Application Server documentation.
When all cluster members in application and support clusters are configured, enable transaction high availability for each application and support cluster. On the Configuration page under General Properties, select Enable failover of transaction log recovery.
Restart the whole environment and make sure that there are no exceptions in the system log files.
When you start a process server that is configured to store transaction and compensation logs in a database, the transaction service can time out while the service waits for the data source to become available. If that happens, you see this error message:
```
WSVR0009E: Error occurred during startup
com.ibm.ws.exception.RuntimeError: com.ibm.ws.recoverylog.spi.InternalLogException: Failed to locate data source, 
com.ibm.ws.recoverylog.spi.InternalLogException: Failed to locate data source
        at com.ibm.ws.tx.util.WASTMHelper.asynchRecoveryProcessingComplete(WASTMHelper.java:176)
        at com.ibm.tx.util.TMHelper.asynchRecoveryProcessingComplete(TMHelper.java:57)
      
```
If you encounter an error of this sort, increase the timeout value.
1. Open the administrative console.
2. Select Servers > Application servers > server name.
3. Under Server infrastructure, select Java and Process Management > Process Definition.
4. Under Additional properties, select Java virtual machine > Custom properties > > New.
5. In the Name entry field, type com.ibm.ws.recoverylog.custom.jdbc.impl.ConfigOfDataSourceTimeout.
6. In the Value entry field, set an integer timeout variable such as 30000 to represent a 30-second timeout. The timeout period is measured in milliseconds.
7. Select OK.

What to do next

Devise a high availability and disaster recovery test plan that is appropriate for the business needs of your organization. The plan might include simulating a WebSphere Application Server ND failover and a cross-database failover to ensure that your system provides adequate business continuity.