Orastack

ORASTACK is another interesting thing that I came across recently. Till now, it was unknown to me hence I thought it will be a useful post.

ORASTACK is an Oracle supplied utility specifically for Windows Operating system. It allows us to modify the default stack size of a thread/session when created in the Oracle executable. It should be run against a specific Oracle binary such as "sqlplus.exe", "tnslsnr.exe" etc. It alters the part of the binary header that defines the default stack size used by "the create thread API".

By reducing the stack of every session created in the Oracle executable, it is possible to serve more users. In a system with a 1000 users reducing the
stack from 1Mb to 500K would release 500Mb of the address space for other
allocations or more users. However if its set too low then session might fail with ORA-3113 error.

It's useful when you get frequent ORA-04030 or TNS-12518/TNS-12500 with ORA-04030 on windows environment.

The usage is -
orastack executable_name new_stack_size_in_bytes

e.g.
'orastack oracle.exe 500000'
'orastack tnslsnr.exe 500000

Remember to shutdown database if changing for "oracle.exe" and for others, ensure that no instance of the process, for which you would run ORASTACK, is running.

Finally a word of caution: - Always consult Oracle support before doing such things for your production environment.