SOLUTION

Deregistering Reports server involved editing the following files 

opmn.xml 


Delete the tag corresponding to the reports server to be removed from ORACLE_HOME/opmn/conf/opmn.xml 
 

targets.xml (for OEM)

Remove the target corresponding to the reports server from targets.xml located under ORACLE_HOME/sysman/emd

<Target TYPE="oracle_repserv" NAME="<ias_instance_name>_Reports_Server: <reports_server_to_be_removed>" ...>...</Target> 

3.Update the changed configuration .
$ORACLE_HOME/dcm/bin/dcmctl updateconfig -ct opmn -v -d
$ORACLE_HOME/dcm/bin/dcmctl resyncinstance -v -d

4. Restart the Application Server Control Console 
emctl stop iasconsole 
emctl start iasconsole

<ias-component id="myrepserver" status="enabled" id-matching="false">  
 <process-type id="ReportsServer" module-id="ReportsServices"> 
  <process-set id="la" restart-on-death="true" numprocs="1"> 
    <environment> 
      <variable id="PATH" value="/home/ias10g/OraHome1/bin:/usr/bin:/usr/ccs/bin:/bin:/usr/kerberos/bin:/opt/IBMJava2-131/bin:/opt/IBMJava2-131/jre/bin:/bin:/usr/bin:/usr/local/bin:/usr/bin/X11:/usr/X11R6/bin"/> 
    </environment> 
    <module-data> 
      <category id="general-parameters"> 
        <data id="batch" value="yes"/> 
      </category> 
      <category id="restart-parameters"> 
        <data id="reverseping-timeout" value="120"/> 
      </category> 
    </module-data> 
    <dependencies> 
      <OID infrastructure="true"/> <database infrastructure-key="portal"/> 
      <managed-process ias-component="OC4J" process-type="OC4J_BI_Forms" process-set="default_island" autostart="true"/> 
      <managed-process ias-component="HTTP_Server" process-type="HTTP_Server" process-set="HTTP_Server" autostart="true"/> 
    </dependencies> 
    <start timeout="120" retry="3"/> 
    <stop timeout="120"/> 
    <restart timeout="120"/> 
    <ping timeout="30" interval="30"/> 
   </process-set> 
  </process-type>
 </ias-component>