I have encountered several times in WebLogic 12c that when the ConnectionPool of a DataSource in WebLogic could not be initialized because due to a connection error or invalid username or password, the server could not be started.

I can't remember having encounterd this problem in 11g, and this week I struggled with it with one of my customers. The perception of the DBA there was that in 11g the server did start up, but the DataSource would go in Suspended-state. Half a year ago, one of the admins just removed a datasource because it made the 12c WebLogic server unstartable. "Taking a short turn", we would say in Dutch.

Now, having a database that is down is a reality at my customers. At least in development and test environments. Also at some of my customers it is a reality to have databases refreshed with an earlier clone. Causing for instance database passwords becoming invalid. It's quite inconvenient not being able to start the servers. Especially when the AdminServer can't be started because of it. And with SOASuite and OSB this is a reality since some of the consoles and composers are targeted to the AdminServer.

This week I found there were 2 options to get the server started:

• Temporarily untarget the datasource
• Set the initial and minimum connections to 0. 

The first was acceptable for one of my customers because they have just one cluster to which the problematic datasources was targeted to. Untargeting would leave all the other settings. And retargetting doesn't raise questions because there's only one target option.

But in a complex domain with several clusters it might not be too obvious to which cluster(s) or server(s) the datasource should be retargeted.

Changing the initial/minimum connections is not ideal either. Because you need to remember what the preferred settings were. These are important when using them for web applications or services used by web applications where performance is key.

But today I stumbled upon a third option: 'Connection Creation Retry Frequency' which can be found under DataSource -> Configuration -> Connection Pool -> Advanced:

Set this to 300 to have a retry every 5 minutes. It is described as:
The number of seconds between attempts to establish connections to the database.

If you do not set this value, data source creation fails if the database is unavailable. If set and if the database is unavailable when the data source is created, WebLogic Server will attempt to create connections in the pool again after the number of seconds you specify, and will continue to attempt to create the connections until it succeeds.

When set to 0, connection retry is disabled.'

Learning all the time...