After delete a user, you can reuse userlogin in OIM. Please follow the steps below.
Step 1: Login system admin screen and click on "System Configuration"
Step 2: Search and find "User Id Reuse property" and set value to "TRUE"
Step 3: Connect OIM database and find "UDX_USER_LOGIN" index and copy its sql script.
Step 4: Drop index.
Step 5: Recreate index as nonunique index.