topic Re: DB05 transaction in Application Development and Automation Discussions

DB05 transaction

Former Member — Thu, 29 Jan 2009 13:08:57 GMT

Dear All,

Do you have any idea what DB05 transaction does and it helps us in some way to improve the performance of the program?

Please let me know if you have some documentation about this transaction.

Regards,

Tarun

Re: DB05 transaction

ThomasZloch — Thu, 29 Jan 2009 13:14:34 GMT


* ------------------------------------------------------------------
* Report rsdb0005 (Transaction DB05)
*  this report calculates the selectivity of an index

It shows the distribution of distinct values for a given combination of fields of a given table, helps you decide whether a secondary index would be efficient.

Thomas

Re: DB05 transaction

Former Member — Thu, 29 Jan 2009 13:17:28 GMT

Hello Thomas,

How do i determine if secondary index is helpful or giving good results by looking at DB05 transaction?

Regards,

Tarun

Re: DB05 transaction

Former Member — Thu, 29 Jan 2009 13:21:13 GMT

Hi Tarun,

Please check the below links,

Best Regards.

Re: DB05 transaction

ThomasZloch — Thu, 29 Jan 2009 13:27:16 GMT

Good selectivity is when by specifying the key values the returned rows can be reduced significantly, to a small fraction of the overall number of rows in the table.

DB05 shows you the number of distinct values and the distribution. The more distinct values, the better.

Try with table EKKO:

- run for primary key: perfect selectivity (no surprise, it's unique after all)

- run for MANDT and BUKRS, well...

Thomas

Re: DB05 transaction

Former Member — Fri, 30 Jan 2009 11:10:07 GMT

Hi,

but be careful, there is biig difference between DB05 and optimizer evaluation of selectivity!

Assume the index has 2 fields:

The DB05 shows the number of different values for

field1 and for the combination (field1, field2)

The optimizer sees usually only the number of different values for

field1 and field2.

It assumes the (field1, field2) has #field1 * #field2 different values. This is usually

different from the actual number.

That is the difference, and the DB05 shows also a part of the distribution of the values,

wether there are values which are taken by many records, i.e. whether the distribution

is unequal.

=> this function makes the DB05 slow.

The actual use case for the DB05 is the test for buffer settings.

If you need the statistical values, then better check the ST05, call data with the Se16 and

trace it, the ST05 shows the statistics for IBM and Oracle databases. In Microsoft and Max DB

the values are not shown.

=> Check DB02, in new releases it also shows statistics.

Siegfried

.... break to be continued ...

Re: DB05 transaction

Former Member — Wed, 04 Feb 2009 11:47:42 GMT

Hi ,

From DB05 transaction you will come to know about the table records according to the primary key and client . You also able to know about the buffering .

If you want to know about the contents according to specified fields you can specify those fields.

Regards

Pinaki Mukherjee