Hello Birla,
1. Cannot stop SAP app server and database ("stopsap all" command gets stuck with message "Checking ADA Database".
Check stopdb.log, stopsap.log and startsap.trc in $HOME folder of sidadm (usually: /home/sidadm).
Those may contain more information about the root cause.
2. Cannot login via SAP GUI - Hangs with the message "Connecting - please wait".
Chech with dpmon, sapcontrol or SAP MC (SAPMMC) the ABAP workprocess list, i.e. the status of workprocesses. Probably they are busy.
Some help reg. the commands:
dpmon pf=/sapmnt/SID/profile/<instance_profile> l (there is a lowercase "l" letter at the end of command, this will show the long work process list)
sapcontrol -nr <instance nr> -host <hostname> -function ABAPGetWPList
Best regards,
Adam