I have PL/SQL function, which is programmed to sort a set of data. This function work fine without any error, when called directly as a PL/SQL Function.
However, when I call this Function Via a Unix Shell Script, even though the script returns a success code and throws an Out Process Memory Error and function is actually not executed.
I have verified the DB Index spaces and temp spaces, which are more than 50% free spaces
The error you are getting is presumably ORA-04030: out of process memory. This means your process is hitting a memory limit. (like, durr).
Why doesn't it hit you when you call the function in a query? Who can tell? Perhaps you are sorting different amounts of data? Perhaps there are different ambient conditions?
This error might indicate you're running out of RAM but alternatively it could mean you're running out of swap (i.e. disk space). If it is RAM and you have some spare capacity you can increase pga_aggregate_target. If it is swap then you need to get your sysadmin guys on the case.