Re: Partitions expanding above the HWM
Date: Tue, 12 Jan 2010 10:35:26 -0500
All good points :)...
So we have 7 transaction based servers. We have a pull that hits each server, so 7 jobs pull this data into a staging tables that is partitioned by server name. No problem so far. Once the data is loaded there and the transformations happen, the polished data is inserted into the reporting tables and then the old records are removed. We only remove old records if that device has uploaded new records. One of the tables the issue is with is hash partitioned by customer ID. I just looked and last night, my tables reused the existing space. It seems about once a week when they do a full pull/versus incremental that we see the table size take off. If allowed to go for several weeks, we begin to see a pattern. The amount of real space within the 640GB segment is roughly 17GB. Even if we were not commiting our data and the space is not being reused, would it explain over 97% of the space not being reused? I'm baffled, but also I am having trouble trying to replicate the issue. I went back through the process and they are running the same package to load the data whether it be a full load or an incremental load. I don't see any parallel_dml. No direct path loads. I don't see any append hints. I don't find anything in metalink.
Starting to think I should probably open a SR at this point :)
On Tue, Jan 12, 2010 at 10:23 AM, Kellyn Pedersen <kjped1313_at_yahoo.com>wrote:
> OK, I know I'm going off very little sleep this last week, so forgive me
> if I'm just oblivious today...:)
> The main issue is, you are concerned about the free space not be
> re-utilized by the next insert after the delete...
> "INSERT INTO table SELECT * FROM staging_table"
> "DELETE FROM table WHERE EXISTS"
> but I have to ask- Where are you committing your transactions, both
> after the inserts and the deletes?
> If this is running in parallel, until a commit is issued, this isn't goint
> to be seen as freespace and I would foresee continual fragmentation in the
> object. I've always recommended bulk deletes of data separate from and data
> loads, whenever possible. Even with a change in the load process, I still
> often experience blocks that aren't re-used if there is high parallel
> inserts and deletes on an object.
> Again, apologies if I'm missing the point here, but until I perform the
> steps that Surachart listed below, I wouldn't expect the HWM to shrink and I
> would expect it to grow due to the logic in the code.
> Kellyn Pedersen
> Multi-Platform DBA
> I-Behavior Inc.
> "Go away before I replace you with a very small and efficient shell
> --- On *Mon, 1/11/10, Thomas Roach <troach_at_gmail.com>* wrote:
> From: Thomas Roach <troach_at_gmail.com>
> Subject: Re: Partitions expanding above the HWM
> To: "Surachart Opun" <surachart_at_gmail.com>
> Cc: "Oracle Discussion List" <oracle-l_at_freelists.org>
> Date: Monday, January 11, 2010, 7:29 PM
> Thanks for the assistance. The blocksize for the whole DB is 16kb. The
> partition is hash by customer with a sub partition so the range I do not get
> help with, but it is definitely an option. What happens is the insert (and
> we have 7 processes running in parallel, so there is some contention on
> these heavy inserts), then each one cleans up the old copies of the records.
> We only delete old records when new ones are uploaded, so if we insert
> 50,000 records, and only 30,000 of them are updates, then it inserts all
> 50k, then drops the old 30k ones, so we could still have 20k from the old
> run. So as more records are inserted, the old blocks look like swiss cheese,
> but the old space does not appear to be used. With ASSM, I wonder if I am
> hitting some sort of bug because the operations I see don't tell me that it
> is avoiding previously used blocks.
> On Mon, Jan 11, 2010 at 9:13 PM, Surachart Opun <surachart_at_gmail.com<http://us.mc320.mail.yahoo.com/mc/compose?to=surachart_at_gmail.com>
> > wrote:
>> ASSM - PCTUSED is no need (ignore)
>> If you use tablespace (ASSM), you can shrink segment (each partition)
>> ALTER TABLE [TABLE_NAME] ENABLE ROW MOVEMENT;
>> ALTER TABLE [TABLE_NAME] MODIFY PARTITION [PARTITION_NAME] SHRINK SPACE
>> COMPACT; -- shrink segment, but no reduce HWM
>> ALTER TABLE [TABLE_NAME] MODIFY PARTITION [PARTITION_NAME] SHRINK SPACE;
>> -- reduce HWM
>> This case may occur, if you have many insert sessions(and have session to
>> delete HIGH values).
>> But if 640 GB and then shrunk to 17 GB
>> How about block_size in this tablespace? -- I have grew up like this on
>> big block_size(32K)
>> I have some question - How about delete data process?
>> If you delete old day ... you may point to make table partition by RANGE
>> (and then truncate old day)
>> Good Luck
>> Surachart Opun
>> On Tue, Jan 12, 2010 at 5:55 AM, Thomas Roach <troach_at_gmail.com<http://us.mc320.mail.yahoo.com/mc/compose?to=troach_at_gmail.com>
>> > wrote:
>>> 4 node RAC - 10.2.0.4
>>> Linux x86_64 RHEL 5.3
>>> ASSM on the Tablespaces (but the table has PCTFREE of 10 and PCTUSED of 0
>>> "which should be ignored because of ASSM."
>>> Reporting Table
>>> Partitioned by hash into 16 partitions.
>>> Degree of parallel is 1.
>>> PCTUSED 0
>>> PCTFREE 10
>>> Staging Table
>>> Partitioned by server name (7 partitions)
>>> Parallelization is enabled
>>> I am having an issue with a table that is just using way too much disk
>>> space. As of today, it was using 640GB. I shrunk it down to about 17GB by
>>> using the move partition command with update indexes. As data is inserted,
>>> it appears to be
>>> I initially thought I had it when I saw PCTUSED 0, but then I found the
>>> tablespace was ASSM, so this value "should" be ignored. I found the package
>>> that loads this table from a staging table.
>>> What happens is this.
>>> "INSERT INTO table SELECT * FROM staging_table"
>>> "DELETE FROM table WHERE EXISTS"
>>> So, I set up a little test case, and I can't seem to replicate the data.
>>> This is not doing anything with APPEND in this package that does the ETL. I
>>> tested with parallel dml enabled at the session level and that yielded no
>>> results. Does anyone have any ideas what I might be missing? Could this be a
>>> bug with ASSM? Any help would greatly be appreciated as I have banged my
>>> head against the monitor all day (not literally).
> Thomas Roach
-- Thomas Roach 813-404-6066 troach_at_gmail.com -- http://www.freelists.org/webpage/oracle-lReceived on Tue Jan 12 2010 - 09:35:26 CST