Global Temporary Tables (GTTs) in ABAP

Overview

• GTTs are special transparent tables for temporary data.
• Data exists only within a database Logical Unit of Work (LUW).
• Accessible by only one consumer.
• Used to save temporary subtotals, splitting complex processes.
• Lower administration costs compared to regular tables.

Key Characteristics

• Always Empty at Start: GTTs are empty at the start of a database LUW.
• Clearing Required: Must be cleared at the end of each LUW.
  • Automatic deletion at the end of a LUW (commit or rollback).

Usage in ABAP Dictionary

• Table Category: Specified as global temporary table.
• Additional Rules: Ensure platform-independent behavior and prevent unexpected responses.
  • Explicit Clearing Required:
    • Use DELETE FROM dbtab without WHERE for clearing.
    • Use explicit commits and rollbacks (COMMIT WORK, ROLLBACK WORK).
    • Runtime error COMMIT_GTT_ERROR if not cleared before implicit commit.
  • Restrictions:
    • USING CLIENT and CLIENT SPECIFIED not allowed.
• Predefined Settings:
  • Data type and size category ignored.
  • Table buffering not allowed.
  • Logging switched off.
  • Storage type is row store.
  • Delivery class is L.
  • No replacement objects.
  • Key fields limited to 15.

Notes on Usage

• Explicit Clear Required: Prevents errors and makes programs clear.
  • Ensures data is deleted implicitly by the system.
  • COMMIT WORK and ROLLBACK WORK clear all connections, while COMMIT CONNECTION and ROLLBACK CONNECTION only affect specified connections.
  • Only DELETE FROM dbtab without conditions prevents COMMIT_GTT_ERROR.
• Exceptions:
  • Rules apply only to ABAP SQL writes.
  • Using Native SQL or AMDP does not raise exceptions on implicit commits.
  • Advisable to use ABAP SQL for ABAP Dictionary GTTs.
• Filling GTTs:
  • INSERT with a subquery from FROM is efficient.
  • Data requests can be optimized using common table expressions.
• Syntax Check: Strict mode for checking ABAP SQL access.

Example Usages

• Global Temporary Tables, Access.
• Union with Global Temporary Table. Image Example