Re: Will Oracle support file compression under NT3.51?

In article <3uj267$8ea_at_helios.vanderbilt.edu> Randy Fought <FOUGHTRL_at_CTRVAX.VANDERBILT.EDU> writes:
> The new release of the Windows NT3.51 OS has added file compression
>as an optional feature. Will Oracle operate correctly using a disk or
>disks that use an operating system level file compression?
>
> Does Oracle support file compression on any other platforms?
>
>Thanks Randy

All current implementations of Oracle will NOT support compressed file systems on ANY operating system (but support is rumored to be coming). The reason for not supporting compression is because Oracle pre-creates data files when you create tablespaces and NOT dynamically as data is inserted.

Assume the following scenario:

I have a 1 gig disk and I create a 500 M tablespace in a datafile on this disk. Initially this file is almost empty and therefore highly compressable. Lets say it compresses to 10 megs. Now I happily keep adding other files onto this disk until it's almost full. Assume only 1 meg of free space is now left.

Now I go ahead and insert 450 megs into my Oracle table on that disk. Oracle thinks that's okay since it "knows" it has a 500 meg tablespace. The OS gave it to Oracle. But the disk has no room to expand and accomodate the growing compressed file. So BOOM it just blows up in your face. The results are obviously going to be unpredictable but really bad.

Hence Oracle cant support compressed filesystems.

Could someone please add this to the FAQ (which never seems to get posted)

shiraz Received on Fri Jul 28 1995 - 00:00:00 CEST