Could not connect from production application to production database

This problem just happen a moment ago and still fresh i think. Right after i finished my lunch, application sys admin asked why we could not connect from hawaii through sqlplus?

Then i tried to start investigating

ora10g@hawaii:/home/ora10g> sqlplus system@zpacdb

SQL*Plus: Release 10.2.0.2.0 - Production on Tue Mar 4 13:41:05 2008

Copyright (c) 1982, 2005, Oracle. All Rights Reserved.

Enter password:
ERROR:
ORA-00022: invalid session ID; access denied


First i thought something must be blocking the connection. Then i tried to connect from my local and it appears OK, secondly then i checked the listener because my local and the application server using different listnener. again this appears OK when i tried connect from my local using application server listener.

So what is the problem? why we could not connect?

I worked together with application sys admin and UNIX sys admin and they found that the hostname of the application server was changed.

ora10g@hawaii:/home/ora10g> hostname
tahiti

Oh my GOD, hostname shouldn't tahiti, it should be hawaii. So we changed it back as soon as possible

ora10g@hawaii:/home/ora10g> hostname
hawaii


and now we can connect again and continue our live


Have a nice day

FZheng