I installed oracle 10g in EL 5 64 bit. Installation went fine. I can login isqlplus using default user like scott, hr schema.
But not as dba user.. getting error message like , the site says: "iSQL*Plus DBA ".
You have to enable that for dba access. Check the Doc ID :How to connect as sysdba/sysoper through iSQL*Plus in Oracle 10g (Doc ID 283114.1)
Thanks its working.