This is steps is applicable only if you want to do a client copy on the same server.
1- Go to transaction Code : SCC4
2- Select the client you will copy from and click on the copy icon .
3-Go to (Tc: RZ10) and choose the profile (Instance profile) and version (12) then click edit
change the parameter name ( login/no_automatic_user_sapstar … and set value = 0 )
4- Restart the service.
5- Login in the coped client , with User : SAP* and Password : PASS
6-Go to (tc: SCCL) copy from (client 000) , fill other parameters -> with (SAP_ALL) and choose from where you want to copy the client
7- Schedule the job in background.
The following link is helpful :