Discussion:
dump file size w/compression
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John Flynn
2009-04-28 15:30:39 UTC
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Hi.

I am on ASE15 on Solaris. The manual says "If the device file already
exists, Backup Server overwrites it; it does not truncate it. For example,
suppose you dump a database to a device file and the device file becomes
10MB. If the next dump of the database to that device is smaller, the device
file is still 10MB." In my experience this has been true; for example one
time when I increased the number of stripes, resulting in more (but smaller)
dump files, each "new" dump file was smaller than before, but the "existing"
dump files did not shrink. Granted, this might have been on a pre-ASE15
server, I forget. But the ASE15 manual seems unambiguous.

So I was surprised recently when I started using compression, and it
appeared that the dump file actually shrank in place. I don't mind this
behavior, but I was wondering whether this should be expected to happen.

Thanks.
- John.
Bret Halford [Sybase]
2009-04-28 16:00:00 UTC
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Post by John Flynn
Hi.
I am on ASE15 on Solaris. The manual says "If the device file already
exists, Backup Server overwrites it; it does not truncate it. For example,
suppose you dump a database to a device file and the device file becomes
10MB. If the next dump of the database to that device is smaller, the device
file is still 10MB." In my experience this has been true; for example one
time when I increased the number of stripes, resulting in more (but smaller)
dump files, each "new" dump file was smaller than before, but the "existing"
dump files did not shrink. Granted, this might have been on a pre-ASE15
server, I forget. But the ASE15 manual seems unambiguous.t
So I was surprised recently when I started using compression, and it
appeared that the dump file actually shrank in place. I don't mind this
behavior, but I was wondering whether this should be expected to happen.
Thanks.
- John.
Hi John,

As of 15.0.2, backupserver deletes the original file and opens a new
one. If you are on an earlier version and using the "compress::"
backupserver api module, then it may be that has always worked that way,
I'm not sure either way. That doc section was written about the
typical generic backupserver dumps.

The change in behavior was to fix CR 377674 "A 624 error may be reported
in case a database is dumped to an existing file and ASE crashes during
dump operation. " - the circumstances resulted in loadable dump file
that contained a mix of old and new page images

Cheers,
-bret
John Flynn
2009-04-29 18:35:07 UTC
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Hi Bret,
Post by Bret Halford [Sybase]
As of 15.0.2, backupserver deletes the original file and opens a new
one.
Thanks, that explains it perfectly.

- John.

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