REP-0501: Unable to connect to the specified database

Issue:

As found from log file:
REP-0501: Unable to connect to the specified database.
ORA-01017: invalid username/password; logon denied

Root Cause:  issue after attempting to re-install Object Migrator on EBS instance and sometimes for some patches like 12964564 ,13855823 oracle application patch.

Solution: 

solution was to apply patch 16946854.

because , patch describes as below details,

=========================================

This patch only affects customer who are using data groups with custom schemas
attached to a responsibility for request submission.

In this case, the patch is necessary to successfully decrypt the password for
the oracle id associated with the custom schema.

Please restart the managers after applying this patch.

=============================================

Bugs Fixed
The following bugs are fixed by this patch:

16946854 - REQUEST SUBMITTED BY CUSTOM RESP AND CUSTOM DATA GROUP CAUSES FNDLIBR TO COREDUM

and moreover below bugs being fixed by this patch,

Bugs Resolved by This Patch


POSSIBLE FND IMPACT FOR MIXED CASE APPLSYSPUB OR GWYUID PASSWORD
11G PASSWORD CASE SENSITIVITY PROJECT CONSOLIDATION BUG
10138986: 11G PASSWORD CASE SENSITIVITY PROJECT CONSOLIDATION BUG
QRE1220.11:GSI:FAILED - LOGIN PAGE NOT LAUNCHING AFTER 12.2 UPGRADE
12937670: 10138986: 11G PASSWORD CASE SENSITIVITY PROJECT CONSOLIDATION BUG
FNDCPASS: REGRESSION OF PASSWORD PROMPTING FEATURE
REQUEST SUBMITTED BY CUSTOM RESP AND CUSTOM DATA GROUP CAUSES FNDLIBR TO COREDUM
SYSTEM HOLD FOR SERVICE PROCESSES.
R:ICM IS DOWN IN ATG121D7.PLEASE BRING IT UP
ACTIVE DATA GUARD SUPPORT: CONCURRENT MANAGER

Try it hopefully it will take you ahead ..... :)