Re: Export/Import to tape?

In article <1993Jan22.200037.1902_at_spectrum.xerox.com>, rdutc_at_sarek.xerox (Ray Dutcher) writes:
> Compressing the export through a named pipe worked great and I did the
> reverse fine without any loss of data. I also did this with success on data
> files (ie. a physical backup). Thanks for the info. Just to check I called
> Oracle Support to see if they > were familiar with this technique and they
> said that they know of customers who do this but they know that some
> customers have experienced a loss of data when using the UNIX
> compress/uncompress command and that Oracle will not support this technique.
>
>
>
> also used compress in the past on exports to transfer a database to another
> machine over my network and also had zero problems.
>
> Before I put this technique into a production system I would like to know if
> anyone has experienced the "data loss" that Oracle Support mentioned? and if
> so please state your Oracle version and OS when replying.
>
> FYI, here's the technique I'm referring to:
> (1) Compressing export to disk
> mknod ora_export.dmp p
> nohup compress < ora_export.dmp > ora_export.dmp.Z &
> exp / ...... file=ora_export.dmp
>
> This lets you compress on the fly without using any disk (well,
> you will use 4 disk blocks or the size of a pipe).
>
> Thank you for any responses.

The problem with using compress that Oracle is refering to seems be related to zcat rather than compress itself. For more infor, refer to document #99769.561. This doco be found on the RTSS BBS.

#     zcat outputfile.Z | dd bs=16K of=/dev/xxx
# 
#     where of = output file (raw device, in our case)
#           bs = block size of conversion
#     (Recall the all compressed files have a .Z extension to them.)
# 
#           What we found was that zcat was deleting blocks when
# uncompressing the files. Thus the database was corrupted due to
# missing blocks.

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