|
The bottom line is that since disk defragmenters are not Oracle
software we do not support them (there is an article along these
lines in the Oracle7 info made available by WebIV in the UK at
http://www-sup.uk.oracle.com/cgi-bin/iv/do.pl). We do not
officially make any recommendations one way or other other on
their use anywhere I've ever seen though.
Disk defragmenters are like any software and the best rule of
thumb is to treat the other software companies the way we want
to be treated (e.g. do you have a reproduceable case, are you
up to the latest patch level, etc. although reproducing those
kinds of bugs is most unplesant) ?
The other problem is that even the official DEC-supported defragmentation
product, since it is software, can suffer from bugs that render Rdb,
etal. useless (such as the bug in the movefile VMS primitive many
moons ago).
The best thing you can do is make sure the product 1) doesn't move open
files -- even if they're closed locally but open on another node in the
cluster -- and 2) respects the SET FILE/NOMOVE attribute in the file
header (and personally I like to size my databases correctly and do
a SET FILE/NOMOVE on the whole database so the products will leave the
database alone). It would be unwise to use any product if they
didn't know the answer to these two questions.
Personally I believe that the kind of file traffic that fragments a
disk should be kept on spindles that the database files are not on
simply for performance reasons and that databases should be sized
proactively so that they do not fragment themselves enough to warrant
help from defragmenting software. If you have enough disk space to
do that then you can just have the defragmenters ignore the database
disks. Likewise people should do some kind of quantitative
assessment looking at DIR/FULLs or something to see if file
fragmentation is really an issue for them so they can make an
intelligent decision based on the actual risk versus benefit.
Regards,
rcs
|
| >> <<< Note 5108.1 by NOMAHS::SECRIST "Rdb WWS; [email protected]" >>>
>> -< Unsupported without prejudice >-
>> The bottom line is that since disk defragmenters are not Oracle
>> software we do not support them (there is an article along these
Ahhh, the mysterious word "support" :)
From many years ago, I believe the engineer position on disk defragmenters
is that:
- you may defragment devices which have Rdb database files if
the database is closed (on all nodes).
- you may defragment devices which have Rdb database files if the
database is open AND the defragmenting tool does not
defragment open files.
Database files should rarely need defragmentation so these should not be a
limitation.
I also strongly recommend (really, in all cases:) that a proven backup
*and* recovery/restore strategy be established to ensure database health in
the event there is some type of unanticipated problem.
|