DB hang with some alert message : DIA0 Critical Database Process As Root

DB hang and not to analyse root cause for the DB hung , not able to sqlplus session.

There is no AWR snap generated during the DB hung period.Last snap is 2:30PM@25-DEC-23

Reported DB hang at around 4:50PM@25-DEC-23 , not to get sqlplus session to get root cause.

Attaching alert log for the analysis :

Some message reported

2023-12-25T14:41:30.340216+05:30

1. DIA0 Critical Database Process As Root: Hang ID 571 blocks 869 sessions

   Final blocker is session ID 4249 serial# 12815 OSPID 15891 on Instance 1

   No resolution will be attempted by Hang Manager.

2.2023-12-25T15:02:06.501918+05:30

WARNING: inbound connection timed out (ORA-3136)

2023-12-25T15:05:52.345857+05:30