RDBMS-- Oracle error -449: ORA-00449: background process 'MMON' unexpectedly terminated with error 448

You can encounter this error on EBS 12.1 and above , especially in the plsql 's that are used for authentication purposes.
For example changing an application users' password or in the login phase of Oracle Applications..
Produced error will be something like below;

Oracle error -449: ORA-00449: background process 'MMON' unexpectedly terminated with error 448 has been detected in FND_WEB_SEC.VALIDATE_PASSWORD

The definitions of the errors are as follows;

oerr ora 448
00448, 00000, "normal completion of background process"
// *Cause:  One of the background processes completed normally (i.e. exited).
//         The background process thinks that somebody asked it to exit.
// *Action: Warm start the system.
 oerr ora 449
00449, 00000, "background process '%s' unexpectedly terminated with error %s"
// *Cause:  A foreground process needing service from a background
//          process has discovered the process died.
// *Action: Consult the error code, and the trace file for the process.

So, an error 449 is produced because of the error 448, which means our foreground process(LOCAL=NO) needs MMON but MMON background process acutally had been exited already.

Also when this error is produced,  if you check the existence of mmon process , you will see that it s not there.. (ps -ef |grep mmon)

Best way to fix this error is to restart application and database services, as suggested by Oracle Support.
Also MMON trace can be gathered to check out the root cause --if necessary, but Oracle Support says that this problem can be faced in EBS 12.1 e nvironments, and it is because of a process lock , so restarting app+db services should be enough to fix it..