while running a program in 1 window (long running ops) ,not able to compile program unit in other.
it is understandably that feature remains from the "days" of PLSQL Dev being connected to one DB instance and one DB instance only, but since IDE can have multiple connections, that feature becomes annoyance.
Of course, another instance of IDE can be instantiated, but was not the intent of multi-connections feature to be able to use 1 instance of IDE being connected to multiple DB's?
So, can you please make such feature configurable.

It is.
Check Preferences.

As IvanZ wrote, you can unlock the ability to compile code when other window is executing.
It's not locked by default because of historical reasons (having only one connection/session). It's locked by default because the code you have executing may block the compilation or even (in some cases) cause deadlock between those two operations if they are executed on the same DB.

I agree that this lock could be more intelligent and do not block the compilation if the execution is done on different DB but determining if it is a different DB is not trivial (as you can have many TNS names for the very same DB).

[quote=Hilarion]I agree that this lock could be more intelligent and do not block the compilation if the execution is done on different DB but determining if it is a different DB is not trivial (as you can have many TNS names for the very same DB). [/quote]

And don't forget distributed transactions.

Yes, that's much more important and complex case.
There's also Oracle RAC and probably many other cases where it can bite you.