I've been thinking a lot about our tablespace layout for our
data warehouse. Our warehouse is approaching 200Gig
and is almost out of space on disk. I'm getting another 75 Gig
this weekend and am trying to plan the best use for that 75Gig.
Our current data tablespace layout is that we have two tablespaces
for small, medium, and large data tables and the same for indexes.
So it's something like this:
SM_DATA01
SM_DATA02
MED_DATA01
MED_DATA02
LG_DATA01
LG_DATA02
SM_IDX01
SM_IDX02
MED_IDX01
MED_IDX02
LG_IDX01
LG_IDX02
I think that theoretically, all of the tables in each of the tablespaces
were supposed to have the same sized extents when they were
originally created. However, over time, there are multiple sizes
of extents in the large and medium tablespaces. Even though we
show significant free space, it is fragmented and coalescing can
not put together enough contiguous space to reuse a lot of the available
space.
Our largest tables are partitioned. However the partitions are not split
out into separate tablespaces but go into the same medium and large
tablespaces as non-partitioned tables. Theoretically, I suppose that this
is not a problem if, when partitions are dropped every month, the resulting
space is reused 100%. I'm not sure if it is.
Here is my question. My DBA team members feel that it's fine to have
tables with a variety of extent sizes in the same tablespace as long as
they are all multiples of each other (50, 100, 400, 2000, etc.). My
concern
is that this setup is fine when the smaller tables need to extend but when
the larger tables need to extend, they can't pull together enough
contiguous
space and I keep having to add more. I'd prefer to have only one size of
extent in each tablespace and keep it very pure that way. Then I know
every single extent can be reused. So I am considering increasing the
number of tablespaces so we have something more like this:
1kdata
10kdata
100kdata
1mdata
10mdata
100mdata
1000mdata
1kidx
10kidx
100kidx
1midx
10midx
100midx
1000midx
I would also probably split them out into at least two tablespaces for each
level.
Maybe not for the smaller sizes, but for the larger sizes.
I have several issues I'm trying to keep in mind. One is the ease of
maintenance
for initial creation and ongoing upkeep. I don't want to have too many
tablespaces
if I don't need to. Another issue is mean time to recover. If we lose a
single tablespace,
I'd prefer to have to recover fewer files. The maximum file size we are
using is 2Gig.
We need to keep our recovery time under four hours total.
Probably the biggest issue I'm facing now is the sheer size of the large
tablespaces.
They are so big and bulky that it's almost impossible to reorg them or even
just
clean them up. I think that if I had more smaller tablespaces, I would
have more
options. This database is still at 8.0.4 and it's going to be a while
before it can be
upgraded so that limits my options for reorging as well. All cleanup has
to be done
in a series short Sunday windows. I don't have the luxury of a tool for
doing this
reorg so have to do it manually.
Another issue is partitions. We are dropping the old partitions on the
main fact
table once a month. We are not currently planning on dropping any of the
other partitions.
The tables have a variety of partition names and schemes. Some are
partitioned yearly,
monthly, quarterly, half-yearly. There is no consistency. I'm debating
whether I should
split each partition out into it's own tablespace. That would be almost a
hundred tablespaces.
Or just the table that we're dropping partitions on monthly. That would
be about 50 tablespaces.
Or should I just leave them all in the same tablespaces as non-partitioned
tables?
We are using Sun Solaris 2.6 on an E10K. We have EMC disk and Veritas
file manager.
Using version 8.0.4 of Oracle, as I said. Using RMAN and Veritas for
backups.
Any feedback, ideas, suggestions, things to watch out for, think about,
etc. would be greatly
appreciated. This is going to take a lot of time and effort to do and I
don't want to get all the
work done and find out it doesn't work as well as I hoped and have to redo
everything.
Thanks for your time,
Cherie Machler
Oracle DBA
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