fork? and retension? 2

[bonsky]

hi! kinda the confuse with these two words.. would somebody help me understand what "fork" means in AIX and how it happens? Also, when using tape drive, what do you mean by retension yes or no in rmtx.y ,i know that theres quite a couple of options here.... but what does retension referring to?
Thanks a lot for your help!

 

[MikeLacey]

fork is a system call, you use it when you are writing programs in C, or some other language

It makes the operating system (UNIX) create a copy of your currently running program (the one that called fork).

This copy (called a child) then goes and does some job that you want doing, that you don't need to specifically wait to see finished, while your original program (the parent) carries on undisturbed.

When the child has finished it can send a message to the parent to let it know it's finished. Mike
michael.j.lacey@ntlworld.com
Email welcome if you're in a hurry or something -- but post in tek-tips as well please, and I will post my reply here as well.

 

[MendotaGuy]

On the second part of your question about the tape retension...
From

http://www.rs6000.ibm.com/doc_link/en_US/a_doc_lib/aixbman/baseadmn/tape_special.htm

(hopefully that will take you to the right place).

Retensioning means winding to the end of the tape and then rewinding to the beginning of the tape to reduce errors. If retension-on-open is selected, the tape is positioned at the beginning of the tape as part of the open process.

rmtx and rmtx.2 - rewind on close
rmtx.1 and rmtx.3 - no rewind on close
rmtx and rmtx.1 - no retension on open
rmtx.2 and rmtx.3 - retension on open

Hope this helps.