The j2c.properties file is used to specify fine-tuning parameters of the JCA connection management runtime. It is interrogated by various parts of the pool manager and connection manager. If the file is not found, or if a particular value is not found in the file, suitable default values are used.
To configure additional database connection settings, edit...$WAS_HOME/properties/j2c.properties
You can enable connection pretesting, which helps to ensure that applications obtain valid database connections from connection pools.
After modiying the file, stop and restart the server.