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It depends on what is going on in the system during those three hours. If this is a regular happening after an IPL, my first thought would be that the system wasn't shut down properly. It's trying to do a full recovery after startup.
But that's just a first impression. Without knowing what's going on, it'll be just a series of guesses.
We can't know that unless the process of "shutdown is normal" is described. Please give details of how your "shutdown is normal" is done. What commands are run in what sequence. Include any timing between commands.
After we know what commands are run for your normal shutdowns, we might need details of what is running at the times that your shutdowns are started.
the shutdown was normal .
For us, the problem is that there is no such thing as a "normal shutdown". There are only 'proper' shutdowns, and each system has its own requirements for what is 'proper'.
We don't know what you do to shut your system down. And until we know what commands you run, we can't help any more than this. We need to figure out what is 'proper' for your system.
The startup program won't help much until we know what problems are caused during shutdown. E.g., index recoveries will have nothing to do with a startup program.
but i think it is related to system value
It could be, but it doesn't seem very likely if it continues for as long as two or three hours. And unless we know what the system is doing, we can't.guess about other things.
The starting point for startup performance problems that continue for hours is the shutdown.