Troubleshooting when the SAP application is down

At times the application may be unavailable or have "crashed" , in this case you do not have the advantage of using SAP GUI tools or transactions to check for the logs since you cannot even log into the SAP GUI!

A good point to start would be to check whether the SAP and Database processes are running in the OS and the available.log file in /usr/sap/<SID>/DVE*/work directory On UNIX platforms and "grep" command can be used while in Windows the task manager would be a good place to check. E.g in UNIX ps -ef | grep sap , if SAP is running then there should be many processes with process IDs and username <SID>adm and for database e.g ORACLE use ps -ef | grep ora 

If few or no SAP processes are listed you can try to restart SAP plus the DB and check the startsap log file and startdb log file in the /home/<SID>adm and /home/ora<SID> directories consecutively.

Depending on what you find from the log files and above steps , various solutions may follow. But other checks you may have to do is check the database listener if it is running , (as orasid user ./lsnrctl status )

Or check if the database is actually mounted and open ( at SQL> prompt select some data from TAB).

***another tool i found to give very useful information is the R3trans -x command on UNIX