Before doing a client copy, you need to prepare the following :-

1. Find the source client space with the client size custom program which can be implemented using the rel. note: 
    Find the space of the client - '0118823'. This will give you the size of the source client. 

2. If your are on Unix OS, adjust all the file systems according to PRD file system to fit the PRD client in DEV 
    client based on space requirements also. 

3. You can do the client copy by remote or export/import client. 
    Remote method is not preferred if you are doing a large client copy. 
    Do a client export/import. 

4. To speed up the export/import, use R3trans export/import for the clustered tables. 
    Please find the rel. notes related to performance improvements for cluster tables in OSS.

5. Do import and post processing. 
    Note: Export may take 10 to 20 hr. for 50gb of data 
    import may take 4 days and post import will take 8 to 15 hr. for 50gb of data. And it all depends on
    your system performance. 

Please refer OSS rel. notes for the few RZ10 parameters which needs to be set for cluster tables to speed up the process. 

Note :-

If it is a fresh installation, do this --

1.  SCC4 --> Create client no. and fill other details.
2.  Logon to the newly created client with SAP* and PASS as password.
3.  SCCL --> choose any profile (preferably SAP_ALL), source client 000 and target client <as created just now>.
4.  Preferably do a test run initially to check if it can go well.
5.  As a care check space in databases.

What are step and procedure to create a client & to take a client copy from source to target.

By: Kavitha.G

If you are copying from same system then flow the below steps:

1. Create the client in Tcode scc4.
2. Before that create a logical System in BD54.
3. Login in the newly created client with 
    user Name : sap*  and password  : pass
4. Use the Tcode sccl to copy the client.if you are not familiar with the client copy.  Try a test run and then schedule it in background.
5. You can select the needed profile.
6. To view the log files use the tcode scc3.

If you are using different system then create a rfc connection in sm59.test the connection and then continue from the 1st step
You can also import and export a client.  Use scc7 for importing from the client and scc8 fro exporting from the source client

What is system refresh when and why it is done?

System refresh and client copy can be the same thing.  Normally when you want to refresh a system this normally means refreshing the clients using a client copy like SCCL or SCC8.  

A system "copy" is very different as this is far more involved than a simple "client refresh"
 
Imagine you have a DEV and a PRD system and after 6 months the data in DEV is very old so you would perform a client copy SCC8 from PRD to DEV using a profile that copies the application data from PRD to DEV - it actually deletes the data and replaces it with data from PRD.  If however your DEV system died and needed to be completely rebuilt, you would use "Homogeneous System Copy" - you install the OS, Database and SAP and then process the system copy - which makes a complete copy of PRD (all clients)
 
Client copy - a single client refresh from PRD to DEV - can be just application data, or user data, or configuration or any combination you choose system copy - all clients 100% copied PRD to DEV

The system refersh is nothing but the deletion of the client and replacing the data from other client.   For example : you have clients 100, 200 and 300.  Suppose when you want to refresh the client 100 you remove the client 100 and replace it with 200 0r 300 as per your reqiurement. Mostly the refresh of clients will be happen at the time of development stage.

System Refresh is a simplified term to Client Copy. Client Copy means copying the production client on to the quality to test the real data. As recommend by SAP this need to carried out every 3 months.

The process to carry out the same is as follows:
 1. Create a client on quality system using txn scc4
 2. Create a RFC between Production system and Quality System (need to create on quality system)
 3. Login to the newly created client using sap* and pass as a password
 4. Txn sccl to start the client copy. You can test the client copy by selecting the test run option. (test run will estimate the time taken for the activity).

Tips by : Shriniwas Yannam, Perala

Get help regarding your Basis problems
Do you have a SAP Basis Question?

SAP Basis Admin Books
SAP System Administration, Security, Authorization, ALE, Performance Tuning Reference Books

SAP Basis Tips
SAP BC Tips and Basis Components Discussion Forum

Best regards,
SAP Basis, ABAP Programming and Other IMG Stuff
http://www.erpgreat.com