nohup has a terrible bad performance compared with interactive command, why?

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nohup has a terrible bad performance compared with interactive command, why?

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02-20-2009

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nohup has a terrible bad performance compared with interactive command, why?

I have a strange situation. I'm running a shell script containing several data uploads (using Oracle sqlloader utility). This script is being run on a Red Hat server.

I tried to run it in background:

$ nohup upload.sh &

This script uploads some thousands files. After several hours I checked what the nohup.out was showing and I was quite surprised to see it was very and extremely slow, because it just processed around less than a hundred files. Probably it would took more than 3 days to complete...

I ran the script interactively, I mean direct from command line showing output to screen. Surprise! the script ran several times better that when using nohup, finishing less than an hour.

I suspicted this was because the process using nohup has a slower priority than the one being run interactively. That was not true, both processes had the same priority.

Why this behaviour? I'm not a linux expert. Please help.

Thanks

viniciov

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LEARN ABOUT OPENSOLARIS

script

script(1)							   User Commands							 script(1)

NAME

       script - make record of a terminal session

SYNOPSIS

       script [-a] [filename]

DESCRIPTION

       The  script  utility  makes a record of everything printed on your screen. The record is written to filename. If no file name is given, the
       record is saved in the file typescript. See WARNINGS.

       The script command forks and creates a sub-shell, according to the value of $SHELL, and records the text from this session. The script ends
       when the forked shell exits or when Control-d is typed.

OPTIONS

       The following option is supported:

       -a    Appends the session record to filename, rather than overwriting it.

NOTES

       script places everything that appears on the screen in filename, including prompts.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+
       |CSI			     |Enabled			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       attributes(5)

WARNINGS

       script  can  pose  a  security risk when used in directories that are writable by other users (for example, /tmp), especially when run by a
       privileged user, that is, root. Be sure that typescript is not a link before running script.

SunOS 5.11							    30 Jan 2004 							 script(1)