It is very important to tune heap size with correct values in production.
Default values are minimum 256 MB and maximum heap size of 1024 MB. For production environments the values are ideally around minimum heap size 4GB (4096m) and max heap size 6GB(6144m)
java -Xmx6144m -Xms4096m
Application ServerIn the Administration Console select Servers
Expand Server Type and select WebSphere application servers
Click on the name of your server
Expand Java and Process Management and select Process Definition