Field Swapping in Database Reduces Conversions for (SAP Library

Field Permutation as Compared with the Database Reduces Need for Transparent Table Conversion

Description

In transparent tables, the sequence of fields in the database is changed from that in the ABAP/4 Dictionary if this avoids conversions. The field sequence in the database can therefore differ from the one in the ABAP/4 Dictionary.

Since the database interface transports the contents of the database field by field to the ABAP/4 work area, the field sequence is irrelevant for accessing the database. Thus, ABAP/4 Open SQL also works correctly with permuted fields. There are also no problems when using ABAP/4 Native SQL, providing the fields are explicitly activated. However, accesses of the type 'EXEC SQL. SELECT * ...' can lead to errors and should be replaced with ABAP/4 Open SQL or the fields should be explicitly specified in the SELECT statement.

Advantages

Many changes to transparent tables now no longer lead to conversion and can be executed in the database with less expensive actions.

Non-key fields

Insert: 'alter table add field ...' in the database

Permute: no activity in the database

Key fields
When changing the key fields, the primary index must be adapted.

Insert: 'alter table add field ... not zero; create index ...'

Permute: 'create index ...'
But, Caution: For client-specific tables, the client field must remain in the first position, otherwise the table is no longer regarded as client-specific. The data of all clients would be mixed and could only be recovered from the data backup. If the table is a check table of a foreign key, the key fields can only be permuted after these foreign keys have been deleted.

A non-key field becomes the key field: 'create index ...'

A key field becomes the non-key field: the data is converted to resolve (any) "Duplicate records"

Substructures
If a substructure is included in a transparent table, then extending the substructure by new fields no longer causes conversion, even if the substructure is in the middle of the table.

Further notes

Field permutation allowed the implementation of a very extensive concept for Customizing and the Extension of tables through the addition of customer fields.

An ALTER TABLE ADD FIELD is now made for inserted fields, as previously for appended fields. These fields have ZERO values for the existing records. Please note the option for Not_zero denotation.