• Created automatically when you create a table in SE11.

• Based on the primary key fields of the table.

• Always unique.

• Cannot be deleted.

• Used whenever you do a SELECT ... WHERE on the primary key.

 Example:
For table MARA, the primary index is on MATNR (Material Number).

SELECT * FROM mara WHERE matnr = ‘MAT001’.

2. Secondary Index

• Created manually in SE11 (or SE14) for performance optimization.

• Can be unique or non-unique.

• Useful when you frequently query on non-primary key fields.

• Stored in the database dictionary as Z indexes (MARA~Z01, etc.).

• Too many indexes = bad performance on INSERT/UPDATE/DELETE (because index maintenance consumes resources).

Example:
If you often query MARA by MTART and MBRSH, you might define a secondary index on those fields.

4. Non-Unique Index

• Allows duplicate values for the indexed fields.

• Used mainly for improving performance, not data consistency.

5. Bitmap Index (special, DB-dependent)

• In SAP on Oracle, bitmap indexes may be created automatically for fields with low cardinality (few distinct values, e.g., “Gender”).

• Rarely created manually in ABAP Dictionary, but worth knowing.

Summary table:

Types:

• Elementary Search Help – based on a single table/view.

• Collective Search Help – combines multiple elementary search helps.

• Field Label(s): Short, Medium, Long, Heading.
• Documentation: For developer/user understanding.
• Domain: Defines the technical attributes like data type, length, value range, etc.

• Data type (e.g., CHAR, NUMC, DEC)
• Field length
• Decimal places
• Value ranges (fixed values or intervals)

Domains help in reusing field definitions across multiple tables or structures.

These fields start with SY- and are always available globally in any ABAP program.

They are read-only for most cases (with a few exceptions) and help developers write more intelligent and context-aware programs.

Why Use System Fields?

You can use system fields to:

• · Check return codes after statements (SY-SUBRC)
• · Get current user (SY-UNAME)
• · Get current date/time (SY-DATUM, SY-UZEIT)
• · Control logic flow depending on system response
• · Debug or log useful runtime info

List of Commonly Used System Fields

Events in TMG are used to:

• Validate data before it’s saved.
• Set default values when creating entries.
• Restrict access to rows based on user roles.
• Log changes or trigger custom logic.
• Enforce complex business rules beyond field-level checks.

Where You Configure TMG Events

1. Transaction: SE54 (Table/View Maintenance)
2. Choose: Environment → Events
3. Select your table/view and function group
4. Choose the desired event number and implement the ABAP logic

TMG Events

• Maintain data in custom or standard tables without writing ABAP code.
• Provide a standardized UI for table maintenance.
• Enforce data consistency and validation through events and screen logic.

How to Create a TMG

1. Go to SE11 → Create or open your Z-table.

2. Ensure:

   • Delivery class = C, L, or G (client-dependent or -independent).

   • Table is not pooled or clustered.

   • Table has a primary key.

3. Click on Utilities → Table Maintenance Generator.

4. Enter:

   • Authorization group (e.g., &NC& for none).

   • Function group (create one if needed).

   • Maintenance type: One-step or two-step.

5. Click Create → Save & Activate.

Now, you can maintain the table via transaction SM30.

One-Step vs Two-Step

Why Buffer Tables?

• Speeds up data access (less DB load)
• Reduces network and database traffic
• Improves scalability for read-intensive operations

Buffering Applies Only to:

• Transparent tables
• That are client-dependent or have primary keys
• Typically read-intensive and rarely updated

You can check or set this in SE11 → Technical Settings.

Types of Buffering in SAP:

In SE11, when you create or display a table or structure, under the “Extras” menu → Enhancement Category, you can specify it.

Types of Enhancement Categories: