Tune disk cache | Configure offload location
Control disk cache size
Do not let disk cache grow to an unlimited size. If you run out of disk space because the disk cache is too large, your server will become non-responsive.
Control disk cache size by setting this custom JVM property com.ibm.ws.cache.CacheConfig.diskCacheSizeInGB.
Start with a few GB and gradually increase that if the response time with writing to disk cache and retrieving from it is still within target. This needs to be monitored closely in your load test.