Table buffering - Invalidations vs Changes on ST10

Hello experts,
Could you please let us know what is the difference between the number of "Invalidations" and the number of "Changes" that are registered via ST10 transactions for each table?
We are interested to identify which tables should be unbuffered considering that these metrics hopefully could help us to take a decision, we would like to know what is the basic difference between each of them.
Thanks and best regards,

Hi Rodolfo,
interesting questions:
A change is a DML statement (INSERT, UPDATE, DELET, MODIFY).
A invalidation is flagging an entry (line, region, table) in the table buffer as invalid
because it has been changed.
I suggest to create you own tables (sng, gen, ful), buffer them and run some tests.
I don't know each and every detail since i didn't tested everything here but here are some of my observations.
A change is counted in the DBI and is a (one) change statement. e.g.
INSERT from wa = 1 change
This will lead to 1 invaldiation PER REMOTE APPLICATION SERVER (the local one is updated with the change hence has no invalidation).
As far as i know array statements are counted as a (one) change as well like:
INSERT ... from TABLE
One change would be the UPDATE SET ... .
These statements let to many invalidations in my test (nr. of records / regions to be changed multiplied with the nr. of remote application servers).
To make it more complicated:
we can have invalidations and no changes since:
R3trans or tp might change buffered tables (do invalidations) but record no change in the DBI.
or
if a projection view is changed the change is recorded in the DBI against the view but the the underlying tables
get invalidations as well (like the view) on the remote application servers.
Kind regards,
Hermann

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Dear Anil, Sunil & hari,
Thank you very much for all quick response..
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ragards,
mani

hi,
You get the same in SAP help, but i dont know the link..
SAP Buffering
The SAP database interface enables storage of database tables in local buffers, i.e. the buffers reside locally on each application server of the system. Buffering is especially important in a client/server environment because the access time using the network is much greater than the access time to a locally buffered table.
The flag Buffering allowed must be set in the ABAP/4 Dictionary in order that a table be buffered. The buffering type must also be maintained in the technical settings of the table. Setting the flag Buffering allowed alone does not cause the tables to be buffered!
Whether or not it makes sense to buffer a table depends on the type of access to the table.
The buffering type defines how the table should be buffered.
There are the following 3 buffering types:
X full buffering
P single record (partial) buffering
G generic buffering
no entry no buffering
A number of key fields between 1 and number of key fields -1 must be defined for generic buffering.
X full buffering
Full buffering
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When should you select full buffering?
For tables up to 30 KB in size. If a table is accessed frequently, but all accesses are read accesses, this value can be exceeded.
For larger tables where large numbers of records are frequently accessed. However, if the application program is able to formulate an extremely selective WHERE condition using a database index, it may be advisable to dispense with full buffering.
For tables with frequent accesses to data not contained in the table. Since all records are contained in the buffer, a quick decision can be made as to whether or not the table contains a record for a specific key.
When considering whether a table should be fully buffered, you should take three aspects into account: the size of the table, the number of read accesses, and the number of write accesses. Tables best suited to full buffering are small, frequently read, and rarely updated.
P single record (partial) buffering
Single-record buffering
With this kind of buffering, only the records of a table which are actually accessed are loaded into the buffer.
This kind of buffering requires less storage space in the buffer than full buffering. However, greater organization is necessary and considerably more database accesses are necessary for loading.
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For large tables where there are frequent single-record accesses (with SELECT SINGLE ...). The size of the records being accessed should be between 100-200 KB.
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Generic buffering
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The number of key fields to be entered must lie between 1 and the number of key fields -1. For example, only values between 1 and 5 are permitted for a table with 6 key fields.
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A table should be buffered generically if usually only certain areas of the table are required. The individual generic areas are treated like independent tables which are fully buffered. Please also read the text about full buffering.
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- the contents of the table doesn't change often.
SAP uses table buffering for a lot of their customizing table.
Bypassing Buffer means: skip the table buffer on the application server
and process the sql-request on the database.
The table buffers are automatically synchronized with changes in the
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available in the table buffer. So if you want to be 100% sure that the
data you read is up to date, you must use the option BYPASSING BUFFER.
Please note that there are also SQL statements that implicitely perform
a BYPASSING BUFFER, for example when using a table in a JOIN statement.
regards,
Prabhu
reward if it is helpful.

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Hi Naved,
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PS: Please remember to reward points if the answer is useful.

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Team,
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CDHDR:
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Hello
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Message was edited by: Shounak Mukherjee

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Moderator message: please find available information.
Edited by: Thomas Zloch on Nov 13, 2011 1:29 PM

Hi,
what is the simple meaining if "invalidate" records in table buffering ?
thanks
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Moderator message: please find available information.
Edited by: Thomas Zloch on Nov 13, 2011 1:29 PM

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Table buffering - Invalidations vs Changes on ST10

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