regarding compress

ravi kumar hassan

regarding compress
Hi Folds,

In our shop we are using DB2 v6, on os390. we have both test and prod.
database. when i saw the sysibm.systablepart for all the tablespaces in
test database defined as a COMPRESS = Y but in production database all the
tablespace as defined as COMPRESS = N. why is that so???? is there any
performance issue??? if we defined compress = y. how the data will stored in
db2.... ??? can somebody help in this issue

Thanks
KUMAR


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Bill Happel

Re: regarding compress
(in response to ravi kumar hassan)
Disadvantages of Data Compression:

1) There is some CPU Overhead to compress and expand blocks.

Advantages of Data Compression:

1) Reduces Overall I/O for sequential processing and can also save I/O for random processing. This is the big one. Compression causes more data to be inserted into one block, which means less blocks are needed, which means less I/O is need to need to read less blocks, which means a Performance Improvement.
2) Reduces DASD storage requirements. Less DASD is needed.

The best thing I like about DB2 Data Compression is the Data Dictionary is stored right with the data. It is even unloaded with the data. In IMS, it is separate.

The data portion is compressed. I do not think the index columns are compressed. Does anyone know this for sure?

We use Hardware Assisted Data Compression (HADC). We have a Rule Of Thumb that all tablespaces greater than 100 CYLs are compressed.


Possible reasons you have compression in Test, but not in Prod:

1) You are currently testing compression. Implementing into Production is sometime in the future.

2) Production is on a different DASD (HSM, SAN, etc) which may have it's own compression.

3) You have not had a window of opportunity to compress Production.

4) Someone in authority is scared sh&$less to implement it into Production.

>>> [login to unmask email] 01/05/01 11:18AM >>>
Hi Folds,

In our shop we are using DB2 v6, on os390. we have both test and prod.
database. when i saw the sysibm.systablepart for all the tablespaces in
test database defined as a COMPRESS = Y but in production database all the
tablespace as defined as COMPRESS = N. why is that so???? is there any
performance issue??? if we defined compress = y. how the data will stored in
db2.... ??? can somebody help in this issue

Thanks
KUMAR


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Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.




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Sanjeev (CTS) S

Re: regarding compress
(in response to Bill Happel)
If Compress Y is there for all the tablespaces then i think there should be
for some tablespace in production as well which is a good candidate for
compression. DSN1COMP is there to check the compression issues. However ,
your installation might require to check it actually for the performance
reason.
But YES for all tablespace in Test and NO for all tablespaces in production
makes me think that check out your DDL generator (if u have any) and then
look if it contains some default value posted YES in TEST and NO in
production.

Just a guess for possible mistakes

Regards.
Sanjeev

> -----Original Message-----
> From: Bill Happel [SMTP:[login to unmask email]
> Sent: Saturday, January 06, 2001 3:16 AM
> To: [login to unmask email]
> Subject: Re: regarding compress
>
> Disadvantages of Data Compression:
>
> 1) There is some CPU Overhead to compress and expand blocks.
>
> Advantages of Data Compression:
>
> 1) Reduces Overall I/O for sequential processing and can also save I/O
> for random processing. This is the big one. Compression causes more data
> to be inserted into one block, which means less blocks are needed, which
> means less I/O is need to need to read less blocks, which means a
> Performance Improvement.
> 2) Reduces DASD storage requirements. Less DASD is needed.
>
> The best thing I like about DB2 Data Compression is the Data Dictionary is
> stored right with the data. It is even unloaded with the data. In IMS,
> it is separate.
>
> The data portion is compressed. I do not think the index columns are
> compressed. Does anyone know this for sure?
>
> We use Hardware Assisted Data Compression (HADC). We have a Rule Of Thumb
> that all tablespaces greater than 100 CYLs are compressed.
>
>
> Possible reasons you have compression in Test, but not in Prod:
>
> 1) You are currently testing compression. Implementing into Production
> is sometime in the future.
>
> 2) Production is on a different DASD (HSM, SAN, etc) which may have it's
> own compression.
>
> 3) You have not had a window of opportunity to compress Production.
>
> 4) Someone in authority is scared sh&$less to implement it into
> Production.
>
> >>> [login to unmask email] 01/05/01 11:18AM >>>
> Hi Folds,
>
> In our shop we are using DB2 v6, on os390. we have both test and prod.
> database. when i saw the sysibm.systablepart for all the tablespaces in
> test database defined as a COMPRESS = Y but in production database all the
> tablespace as defined as COMPRESS = N. why is that so???? is there any
> performance issue??? if we defined compress = y. how the data will stored
> in
> db2.... ??? can somebody help in this issue
>
> Thanks
> KUMAR
>
>
> _________________________________________________________________________
> Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.
>
>
>
>
>
>
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> you should not further disseminate, distribute, or forward this
> E-mail message. If you have received this E-mail in error,
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