I got this error when am trying view dba_tables Ora 03113 end of file on communication channel
Error  ORA 03113 end of file on communication  means: The connection between Client and Server process was broken.

Possible causes and general troubleshooting:


Network problems
Oracle internal errors / aborts on the server
Client incorrectly handling multiple connections
check SQL*Net setup
look in the alert.log file for any errors