I have 2 clients in one server.  The database is SQL. 
Would like to perform the backup for each client separately so that I can restore per client. 
So far, I've only found information saying that we have to do the entire backup for the database and that individual client backup is not good. 

Can anyone advise me on how to perform individual client backup and how's the data integrity. 

Sharon 

It little confusing with your statement when you are saying that "I have two clients in server". 
Or is it rather you want to say that you are having two database instaces on one server.

Scenario 1:
You have One server hosting more that one client as you say. Lets assume it to be Developement & Test client on single databse. Here please note that any SAP DB instace always have more than two clients. The Defaulta clients are: 
      * Client 000  : SAP AG Konzen
      * Client 066  : SAP Early Watch Client.

In addition you have your client specified as 
     * Client XXX  : This will be your production / dev / test client

You can have as many client as you want in a system. Well that really depends on amount of workload and the hardware capacity of the server.

Scenario 2:
You have more that one Database instance on single server. Here you have a choice of having same programs files with multiple databases and or having two different databse instaces with saperate program files. Like in case of oracle you can have two oracle instances Oralce 8i and other with Oracle 9i or any combination you like.

Now  your question "Can I take backup of the single client ?"
Ans : Well its possible but then this is not a normal scenario. Its not call as a backup though. You can use the fuctionalities such as client export or client copy procided by SAP.

Second Question : " What about the data integrety ?"
Ans : The option of Client Copy or Client Export are used for specific purpose. You are required to do changes / configure required by the specific fuctionality.

Important Points:
In case of database failuer you would need the complete backup of the database and not just particultal client.
SAP Database does not contain only data but also contains the programs as well. And some of these infomation (Data as you would call) is shared across multiple client in one databse instance. 
Hense it is important to restore the complete databse to retain the integrity of the system.
In case of having different DB instances on server you can perform backup of the individual databases. That is sufficient to bring the individual system up after the database failuer.

Hope this is sufficient for your doubt.

Sachin

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