DSXchange

I am getting the following error message
SQL*Loader-704: Internal error: ulconnect: OCIServerAttach [0]
TrgCcdbUser,3: ORA-12520: TNS:listener could not find available handler for requested type of server

My sequence has 12 jobs when i run the jobs separately the jobs are running fine. but when i run the sequence each time a different job is failling.

Any time you see a problem which only surfaces when running multiple jobs at a time but never does when they run one at a time, that screams "resource issue". I would take that error to your DBA and see what kind of limits your target Oracle instance and/or listener is configured with, sounds to me like you've hit one.