The connection pool goes out of resource is very common issue we usually face across all types of applications. As there are plenty of reasons for the same like application is not closing the connections, concurrent user access of DB resources etc etc.
On Weblogic there is a very nice way to handle this situation in very fast manner using Admin utility. see below steps
Step 1: On Windows set WLS environment using setWLSENV.cmd(wls_home/wlserver.x.x/server/bin)
Step 2: Once environment gets ready, run the below weblogic admin utility.
java weblogic.Admin -url AdminHost:7001 -username weblogic -password weblogic RESET_POOL -poolName
After running this command, you will see a message on console stating the result of the operation.
****Note: This is just a workaround, not a solution, the action must be taken to handle this issue from application perspective, like making sure to close all the JDBC resources.