Since version 8 of WAS, you can emulate High availability of your Data Sources using Alternate data sources. You can configure alternate data sources by simply adding a custom property named alternateResourceJNDIName to your data source. This property contains the JNDI name of the alternate data source.
To enable workload routing among data sources, complete the following steps:
1. Click Resources >JDBC > Data sources and select your desired Data Source.
2. From the data source Additional properties, select the Connection pool properties link.
3. In the Connection pool properties screen, follow the “Connection pool custom properties” link.
4. Once in the Connection pool custom properties screen, click New to add a new custom property.
5. Enter an arbitrary Name for the resource and as Value the JNDI name of your mirror failover Data Source as shown by the following picture:
Click Apply and Save your data to the master configuration and repeat the above steps also on your mirrored failover data source to enable failback to the primary data source. Finally, restart the affected application servers.