abap-performance-ecc

ABAP Performance — ECC / Traditional Database

These rules apply to SAP ECC systems running on traditional databases (Oracle, DB2, MSSQL, MaxDB).

Before writing, optimizing, or reviewing ABAP code, read the abap-code-review-helper skill in full (skip if skill is unavailable), unless its complete contents are already available in your current context. Preserve its correctness safeguards; an optimization must not change result semantics. Keep passed checks internal.

Before using this skill: Call the SAP system info tool. If the system is S/4HANA or HANA DB, use the abap-performance-hana skill instead.

Core philosophy on ECC: Minimize database round-trips. Keep SQL simple — traditional DBs don't optimize complex expressions well. Buffer aggressively. Move complex logic to ABAP.

Database Access

SELECT Patterns

• Select only the fields you need. Never use SELECT * in production code.

  " good
  SELECT matnr maktx FROM mara INTO TABLE itab.
  " bad
  SELECT * FROM mara INTO TABLE itab.
  

• Always use a WHERE clause. Never read an entire table without filtering.

• Prefer JOINs over nested SELECTs. One round-trip is always better than N.

  " good — single round-trip
  SELECT m~matnr t~maktx
    FROM mara AS m
    INNER JOIN makt AS t ON t~matnr = m~matnr
    WHERE m~mtart = material_type
      AND t~spras = sy-langu
    INTO TABLE materials.
  

• BUT keep JOINs simple on ECC. Avoid more than 3-4 table JOINs — traditional DBs may generate poor execution plans. Split into two SELECTs if needed.

• Use FOR ALL ENTRIES when JOINs aren't possible. Always check driver table is not empty.

  IF itab[] IS NOT INITIAL.
    SELECT matnr werks FROM marc
      FOR ALL ENTRIES IN itab
      WHERE matnr = itab-matnr
      INTO TABLE plant_data.
  ENDIF.
  

• FOR ALL ENTRIES removes duplicates from results. Add extra key fields if you need duplicates.

• Use UP TO n ROWS when you only need a limited result set.