one possibility comes to mind:
there is not enough room in the original directory for the uncompressed
file and the compressed one (both exist while the uncompress is
running)
- Pat Howe <PHowe_at_verisign.com> wrote:
> I am trying to work thru the one of the scripts that I inherited and
> I was
> wondering if someone could shed some light on why the author used a
> UNIX
> PIPE to uncompress a file.
>
> Code :
> mknod /tmp/testdb_data_01.dbf_pipe p
>
> uncompress < /tmp/testdb_data_01.dbf_pipe >
> /u06/oracle/oradata/testdb/tbs/data_01.dbf &
> sleep 1
>
> cp data_01.dbf.Z /tmp/testdb_data_01.dbf_pipe &
>
> Background :
> File 'data_01.dbf.Z' exists in compress format.
> We are currently in the directory where this file resides.
>
> My Confused Analysis :
> line 1 : creates a pipe file called 'testdb_data_01.dbf_pipe' in the
> '/tmp'
> directory
> line 2 : In the background we start to uncompress from the 'PIPE
> file'
> (FIFO) into my destination directory
> '/u06/oracle/oradata/testdb/tbs/data_01.dbf'
> line 3 : Puts the script to sleep for 1 second (no idea why)
> line 4 : In the background it copies the compressed file
> (data_01.dbf.Z) to
> the PIPE
>
> Therefore as the copy occurs (line4) - the PIPE (using a
> First-In-First-Out)
> starts to uncompress my file (line2).
>
> Question :
> What does this gain me ? Ie ; Why would the author do this ?
> Seems to me to be alot of additional IO copying the file to '/tmp'.
> Why not just uncompress the file directly to its destination
> directory
> (/u06/oracle/oradata/testdb/tbs/) ?
>
> Thanks in advance
>
> _________________________
> Patrick J. Howe
> Oracle DBA
> VeriSign, Inc.
> 4501 Intelco Loop SE
> Olympia, WA 98507
> Phone : 360.493.6284
> Email : phowe_at_verisign.com
>
>
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> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Pat Howe
> INET: PHowe_at_verisign.com
>
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Received on Wed Aug 14 2002 - 20:28:31 CDT
