What is MustGather script ?

If you face any performance degradation, hang, no response, hung threads, CPU starvation, high CPU utilization, network delays, or deadlocks, this MustGather will assist you in collecting the critical data that is needed to troubleshoot your issue.

Use below link and download MustGather document as per your environment.

http://www-01.ibm.com/support/docview.wss


MustGather: Performance, hang, or high CPU issues on Windows

Step 1 : Download the windowsperf.jacl script. This script works for WebSphere Application Server version 6.1 to version 9.1.

windowsperf.jacl

Screenshot :

Step 2 :  Use below command from WebSphereApplication home\bin:
Syntax :
wsadmin -lang jacl -javaoption -Xmx256M -f <path to file>\windowsperf.jacl servername <nodename if needed> 

Screenshot :

Step 3 : Check the javacore files of same server.

Screenshot :






















Step 4 :Check the set of javacores, tasklist, netstat, and some performance.

Screenshot :

Note: the number of iterations and the pause time between collections are the first 2 executable lines in the script, The variable iters is the number of iteration and the ptime variable is the pause time .
normally this is set to 3 iterations and 120 second ptime as below: 
set iters 3
set ptime 120



Ref doc : https://www-01.ibm.com/support/docview.wss