Workflow :: Update Mail Attribute In OIM / OID

we are trying to update the Email attribute in OIM followed by OID. we have written a scheduler to copy the username field to email field in USR Table through tc User Operations interface, followed by change email task and update email task to OID.

But it is taking 1 hour for 1000 records to finish the job. we have 200000 Users in Production, Is there any better approach I can fasten the process? we are having an idea to update the USR Table through SQL Querry for OIM Side. And when we tried to update the CT_MAIL table in OID. But it is not showing the values in the front end ODSM.

Now thinking to write a scheduler separately for OID by just connecting to ldapctx, update each records and disconnect finally after updating all the operations.

OIM Version : 9.1.0.2
OID Version: 11.1.1.3.0