DB hung as archive was filled up

I am back to basic but very curious to know how db version 9.2 bahved.

I was trying to shut AN instance

shutdown immediate and it just hung. There were no users and no tranactions.

After waiting for about 7 mints, I opened new session and I executed kill -9 PMON

First session ended. I started the instance and got error like

ORA-16038: log 1 sequence# 100 cannot be archived

ORA-19502: write error on file "", blockno (blocksize=)

ORA-00312: online log 1 thread 1: '/xxx/u50/oralog/redo01a.rdo'

ORA-00312: online log 1 thread 1: '/xxx/u51/oralog/redo01b.rdo'

I saw this and knew it was space. So I cleared archive space and I could startup and shutdown normally.