OID : Deleting OID/OPMN instances

One can face weird issues due to OID Instances not being deleted the right way. Simply deleting them from the file system or from OID might not be enough as there are entries that stay on the ODS Schema of the Database.
This can cause unforseen issues like delay in OID restarts (ldapbind fails for few mins even though instance shows up as ALIVE) or weird issues like referential integrity working intermittenly in OID/OIM.

It is highly recommended to remove an Oracle Internet Directory component by using opmnctl deletecomponent. This also unregisters the component with the WebLogic server.

Syntax :

$ORACLE_INSTANCE/bin/opmnctl deletecomponent
  -adminHost webLogicHostName
  -adminPort webLogicPort
  -adminUsername weblogicAdminUsername
  -adminPasswordFile text_file_containing_admin_password
  -componentType OID
  -componentName componentName

Sample for removing an instance named oid4
export ORACLE_INSTANCE=/u01/app/oracle/admin/config/oid_inst_3/
$ORACLE_INSTANCE/bin/opmnctl deletecomponent \
  -adminHost <wl_server_Name> \
  -adminPort 7001 \
  -adminUsername weblogic \
  -adminPasswordFile adminpass.txt \
  -componentType OID \
  -componentName oid4

Reference - https://docs.oracle.com/cd/E16764_01/oid.1111/e10029/oid_server_instances.htm#BABDJABF

OAM 11gR2 : 500 Internal Server Error after registering new 11g Webgate

I got the error as in the subject after I had registered a new webgate , done other necessary configurations and tried to access a WebCenter Portal page which I was trying to protect.

The error in the oblog.log said - 

Request Failed for : /index.html, Resp Code : [500]

OBWebGate_AuthnAndAuthz: Cannot get message for ObAccessException_NO_AGENT_KEY

Oracle Support had a similar issue for Fusion Apps which didnot really help -

https://support.oracle.com/epmos/faces/DocumentDisplay?id=1534423.1

Finally , after using the OAM Tester , a colleague suggested to edit and re-copy Webgate related files from Output Directory of the OAM_Domain pertaining to the webgate to <OHS_Instance>/config/OHS/ohs1/webgate/config.

Hope this helps someone facing a similar issue.