Ping JVM comes and site becomes unavailable

After Every few hours we get following errors:

Pinging the JVM took 34 seconds to respond. Pinging the JVM took 25 seconds to respond. Pinging the JVM took 16 seconds to respond. Pinging the JVM took 7 seconds to respond.

Pinging the JVM took 38 seconds to respond. Pinging the JVM took 29 seconds to respond. Pinging the JVM took 20 seconds to respond. Pinging the JVM took 10 seconds to respond. Pinging the JVM took 1 seconds to respond. site becomes unavailable during 1-2 minutes (no reports at this time isn't written to logs);

then several messages "Pinging JVM ..." appears in the log and site becomes available;

there is "No Data available." message in "Sessions overview" section in hac;

Java takes almost the entire memory.

What could it be? What should we do to solve this problem?

Please find the below memory and cache settings that we have :

regioncache.entityregion.size=500000 regioncache.querycacheregion.size=200000
tomcat.javaoptions=-Xms4G -Xmx12G tomcat.generaloptions=-server -Xms4G -Xmx12G -XX:PermSize=500M -XX:MaxPermSize=500M -Xloggc:../logs/java_gc.log -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+UseParallelGC -XX:+UseParallelOldGC -XX:+UseAdaptiveGCBoundary -XX:+ExplicitGCInvokesConcurrent -Dsun.rmi.dgc.client.gcInteraval=3600000 -Dsun.rmi.dgc.server.gcInterval=3600000 -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=${tomcat.jmx.port} -Dcom.sun.management.jmxremote.ssl=false -Dorg.tanukisoftware.wrapper.WrapperManager.mbean=true -Dcom.sun.management.jmxremote.authenticate=false