How lock unlock client in sap to prevent user login

This is a workaround to lock a client to prevent user to login during patching or any maintenance activity of SAP R/3 (ECC 6.0). Example with detaile are given below:-

Client locking:-----------
SE37->SCCR_LOCK_CLIENT
Press  Run/Test (look like ZIP file button)
enter your Client No. i.e. 210/300/500/900 etc
Press Execute button only.
Done

Client Unlocking:-----------
Client lock-> SE37->SCCR_UNLOCK_CLIENT
Press  Run/Test (look like ZIP file button)
enter your Client No. i.e. 210/300/500/900 etc
Press Execute button only.
Done

Best of Luck