Configure a Max Threads Constraint and add your application to the list of applications for the Constraint.
Configure a Work Manager with a Maximum Threads Constraint tied to the Connection Pool and configuration your application to use the Work Manager.
Configure a Work Manager with a Minimum Threads Constraint tied to the Connection Pool and configure your application to use the Work Manager.
Configure a global MaxThreads constraint and target it to the server or clusters where your application is deployed.
Configure the startup parameter -Dwls-maxThreads to be the same as the number of database connections configured.