There will be no need to End the sub systems for taking the backup of the system. But, You should make sure that, No Jobs(Which will affect backup process) will run at the time of Backup.

Pradeep.

but deepu i read in a book that we should end subsystem when doing backup while using command SAVSYS

Yeah. I misunderstood the question. I was thinking in a view of SAVSTG, SAVLIB, SAVSECDTA Commands.

The Save System (SAVSYS) command saves a copy of the Licensed Internal Code and the QSYS library in a format compatible with the installation of the operating system. It does not save objects from any other library.
And, As you mentioned, All subsystems must be inactive before the SAVSYS command can be specified.

But, The same will not be needed in case of other commands like SAVLIB & SAVSECDTA.

For SAVSTG Command also, All the SubSystems must be ended except in which the Job(SAVSTG) in running. No other Jobs should be running.

Pradeep.

so for all the SAVxxx we should end the subsystems, isit deepu?

you will only end subsystem when you are doing full backup.

should we end all the subsystem for all backup methods

You only need to end all subsystems for backups that require all subsystems to be ended. The help text for each command tells you if restricted state (all subsystems ended) is required.

Tom