Re: ASSM and tablespace fragmentation in a table that adds 140,140 partitions/subpartitions per year
- From: Dba DBA <oracledbaquestions@xxxxxxxxx>
- To: ORACLE-L <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 7 May 2013 13:58:12 -0400
We add and drop 140,140 partitions/year.
I meant let oracle pick the extents or I pick them. I got a little mixed
up on ASSM. I noticed something odd with uniform extents ( i have not used
these in years).
I have 8k block sizes. I set uniform extents to 1mb. I noticed that my
extents are actually 8mb. I can tell these because when I create the table
and get the initial set of partitions, I can see the 1 extent per
partition.
so extent size with uniform is the size you set times the block size? This
is in 11.2.0.3
I used 'uniform extent size 1mb' and got 8 mb extent sizes when I look in
the database. This is before any data is in the table.
On Fri, May 3, 2013 at 6:44 PM, Mark W. Farnham <mwf@xxxxxxxx> wrote:
> As far as tablespace fragmentation goes, you can only get that if you drop
> things.
>
> Oh - except for a little bit at the end of each file you maybe can't use if
> you're not using bigfile. (But that can happen with uniform, too, maybe
> worse.)
>
> Also, ASSM can be either uniform or not, as can Freelists. Only dictionary
> managed gives you the opportunity to be truly helter skelter.
>
> -----Original Message-----
> From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
> On Behalf Of Dba DBA
> Sent: Friday, May 03, 2013 3:10 PM
> To: ORACLE-L
> Subject: ASSM and tablespace fragmentation in a table that adds 140,140
> partitions/subpartitions per year
>
> oracle 11.2.0.3
> Since ASSM uses different size extents, are there any issues with
> fragmentation? There was an Oracle-L thread dating from 2007 that discussed
> this.
>
> I have multiple tables that need to be hourly partition and will have 16-32
> (possibly more ) hash sub-partitions. So I will be constantly dding and
> dropping partitions. I did some tests with my hash sub-partitioned and they
> do not appear to be particularly well balanced. The data values I have are
> skewed. (there are 700+ and more get added, so list is not practical).
>
> With hourly partitions and 16 hash sub-partitions I am adding 140,160
> partitions/sub-partitions a year. We really only keep a 4 day window of
> data. So at any time, we will not have that many partitions. I don't think
> the data rate will always be real consistent. I also do not know how
> inconsistent the rate will be on the sub-partitions. I actually won't know
> until it is deployed to production.
>
> is there any reason for me to use uniform extents? These tables are insert
> only. I believe freelists settings only matter if the table gets updates.
> Just want to be safe on fragmentation. Another company runs the production
> database. They probably won't check for this. We also have very high uptime
> requirements with at most 1 hour outages for builds/maintenance (and very
> infrequent).
>
> Also, I cannot use interval partitions. I stumbled on a limitation with
> intervals. Oracle can only handle a total of 1m partitions/sub-partitions
> dating from the root partition.
>
> So even though I am only keeping a 4 day window of partitons, the counter
> starts at the root and keeps going up. So when we hit 1m from the root, we
> can't handle inserts. This gets turned over to another company and its not
> a
> good idea to pass something that would cause an outage. It would almost
> certainly get forgotten over the years.
>
> I don't have the test case any more, but if you are interested...
> create an interval partitioned table by hour. subpartition it with 16 hash
> partitions set the root to the year 2000.
>
> Insert 1 record. You get an exception stating that oracle can only handle
> 1m
> partitions/sub-partitions.
>
> adding this because I am not sure if this increases my chance of
> fragmentation.
> I don't think it matters. So this is probably just background info.
>
>
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>
>
>
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