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Table Buffing Explained

Tuesday, 31 July 2012 12:43

Written by Prakash Palani

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Table Buffering - ST02

 

Buffering Types

Single-Record

 

Single-record buffer (what you see in ST02) contains the data that is needed for accesses that are performed using all table keys of a table, for example, query with all the primary keys specified in the where clause.  The buffering concept works as usual, each record that is fetched from the database for the first time is placed in the buffer, whenever the same record is requested by the query, it can be read from the buffer instead of disk.

 

For example

SELECT SINGLE * FROM USR02 where MANDT='XXX' and BNAME='PALANIP'

 

Not every table in the database will be making use of single-record buffering, only the tables which has single record buffering activated (as shown below) can make use of it.  In addition to that, only the statements which has SINGLE in it can make use of the single record buffer. Essentially the query must contain single and all the primary keys in where clause, only then the data will be stored/fetched from the buffer, else the statement will access the data through the database.

 

 

Full Buffering

 

 

As the name itself suggests, if the full table buffer (as shown below) is activated on a particular table, then the first access to the table will load entire table into the full table buffer. This buffer type should not be used for the tables with larger size, generally it is recommended to activate for the tabels between 1 to 5MB in terms of size. (you can check the same in DB02-> Detailed Analysis (under table).

 

 

Generic Area Buffer

 

Generic Buffer focuses on a number of primary key fields specified in the technical settings, it basically not only buffers the particular data records that is required by a query, but also buffers all other data rows that have same key values as the targeted record.



 

Tip: Need of a complete overview on the buffer settings, have a look at DD09L, this will give you an indication on the type of buffering used for each of the tables.

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Table Buffing Explained