We have 3 types of buffering
There are the following types of buffering:
- single-record buffering
- generic area buffering
- full buffering
When should single-record buffering be selected?
- For large tables where there are frequent single-record accesses (using SELECT SINGLE ...). The size of the records being accessed should be between 100-200 KB.
- For comparatively small tables for which the access
range is large, it is normally advisable to opt for full buffering. Only
one database access is required to load such a table for full buffering,
while single-record buffering calls for a very large number of tableaccesses.
When should generic buffering be selected?
- 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 that are fully buffered. Refer also to the text on complete buffering.
- The generic key area should be selected so that the generic areas are not too small to prevent too may generic areas being produced. If there are only a few records for each generic area, it is more efficient to use full buffering.
- Generic buffering only makes sense if the table is accessed by a specified generic key. If, when an access takes place, a field of the generic key is not supplied with a value, the buffer is ignored and the records are read directly from the database.
- Language-specific tables are an example of good use of generic buffering (with the language key field as generic key area). 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.
