Hanged Processes and ORA-00020, ORA-12518 Error

Question:
We had a problem with our UPS in the backup data center,
whereby 3 of 6 application servers have been without electricity. When we
restarted the Computer is a correctly started (except 3 dialog processes). the
other two report:
    ORA-12518: TNS: listener could not hand off client
When I try to log in SQLPLUS I get the following error:
    ORA-00020: maximum number of processes (string) exceeded
I think the ora-12518 is a result of the error ora-00020th I suspected
is stuck processes.
How can we identify hanged processes?


Answer:
This ORA-00020 problems are caused by insufficient size of number of
session/proces ses on Oracle level. A new connection aborts with error
ORA-00020: maximum number of processes (%s) exceeded.
Ultimately this is the reason why tp does not work.


Please revise the parameters sessions/processes according to the formula
in SAP note #830576 and restart then the database with higher values.
This issue should be then solved and new connections such as from tp
made possible.


Please refer the following notes for more details.
#398927 ORA errors because dimensions of parameters are too small
#34432  ORA-00020: maximum number of processes exceeded


As for error ORA-12518, here are some article found in Oracle Metalink:
371983.1 - 10gR2 Dedicated Connections Intermittently Fail with
           TNS-12518
340089.1 - New Connections to the Database lead to ORA-12518 or
TNS-12518
#758563 Oracle Metalink access for SAP customers