IN AEM WHY backup_.tar files are created

Issue : 

•  AEM Server is taking too long time to stop or not shutting down.

Solution :

• The CRX process should never be killed, also not when stopping takes too long. 
• If you do kill the CRX process, the next time you start it up the Tar PM can create backup_.tar files.

Precaution :

• If you need to kill a process that is not responding, create a full thread dump first.

AEM_How to identify the check session count

Issues: 

• In many cases the problem is the number of open sessions it too large. 
• At some point, it slows down processing. 

Solution :

• To find out if this is the case, run

        jps -l (to get the process id of the Java process)

        jmap -histo  | grep CRXSession (to get the number of open sessions)

Conclusion :

• If no of opened sessions count is greater then some hundred, then there is possibility of session related issues.
• Possibly a session pool is used (depending on the version of CRX / CQ there could be a hot fix for the given problem), 
• or an internal (possibly application level) cache references sessions. To analyze where those sessions are opened.
• Generate thread dump and heap dump to find out the RCA.
• Use the eclipse MAT for heap dump analysis and TDA or fastthread for the thread dump analysis.

AEM_Command to check CPU usage & how interpret the results

• To analyze the problem, it is important to know if CRX /CQ is running in an endless loop, or if it's merely sleeping. To find it out, type

                              top

• This command gets you the list of processes, sorted by CPU usage. 
• If the top process is a "Java process, and if the PID matches CRX/CQ, then the process is running full speed.
• If you are unsure how to interpret the results, run the following statement and then include the file top.txt in your problem report:

                             top -l5 -s5 > top.txt