I have created a user 'uca' with the below command,
useradd -m -d /home/uca -s /bin/bash uca

Now the problem is this user 'uca' is not able to access database. is ther any special group of users which can access the database.?
please help

Since you don't tell us what version/distro of Linux, version of Oracle, or tell us how you're trying to access the database, or even what message(s) you're getting, there's not much we can tell you. Have you contacted your DBA's at your company to ask them, or checked the Oracle website? Contacted Oracle support??

Without details, we can't help.

Are you trying to access it from oracle console ?
i dont know much about oracle but when it has its own admin user and privilages for them, you may need to make another oracle user and "GRANT [permissiosn] on *.* to user@domain " (something like that i remember to use while doing mysql configuration along back) to grant it necessary privilages in order to have it able to access the database for you.

There can be other ways too, but as said in the above post we shld have some more info on what distro/version you are using... and what you are seeing when you try accessing the adatabse along with how you are trying to do it..

Just because you have a Linux user doesn't mean that user can just drop into the Oracle database and start editing data. You also have to create him in the database software as well. Either using OEM or SQL*Plus.

http://docs.oracle.com/cd/B28359_01/...ments_8003.htm
Post the logs from Oracle ... should be /u01/oracle/apps/oracle/$version/...

Did you grant the user a password after you created him? You show your useradd statement however you never enable a password for him. Please explain what version of Linux, release version, kernel, Oracle 11.2.x???

Give us something to help you please...

Each Oracle user must have specific roles granted to him! Each Oracle user MUST HAVE 'connect' ROLE and the 'CREATE SESSION' priv to use their table space assigned to them. You can use OEM (Oracle Ent. Manager) if you can't do it in SQL*Plus.