Measure First: ST05, SAT and Runtime Evidence

Explanation

Good performance tuning starts with evidence. Many developers immediately change loops or internal table types, but the real bottleneck is often database access. ST05 SQL Trace shows expensive SQL statements, number of executions, records fetched and database time. SAT shows ABAP runtime, method calls and processing hotspots. SQL Monitor can help identify frequently expensive SQL in production-like usage. The first question should be: is the time spent in database, ABAP processing, RFC, update task, frontend rendering or file handling? Once the bottleneck is known, the fix becomes targeted and defensible.

Code example

* Performance tuning checklist:* 1. Run the slow transaction/report with realistic selection.* 2. Use ST05 to trace expensive SQL.* 3. Use SAT to identify ABAP processing hotspots.* 4. Check how many times each SQL is executed.* 5. Optimize the biggest bottleneck first. * Key rule:* Never guess. Measure first, then optimize.

Real project scenario

A finance report was assumed to be slow because of ALV formatting. ST05 showed one SELECT inside LOOP executed 48,000 times. Replacing it with one bulk SELECT and hashed lookup reduced runtime from 22 minutes to less than 1 minute.

Common mistakes

- Changing code without measuring. - Optimizing small loops while DB time is huge. - Testing with tiny data volume. - Ignoring SQL execution count.

Best practices

- Use ST05 for SQL trace. - Use SAT for ABAP runtime. - Test with realistic data. - Fix the highest-impact bottleneck first.

Interview angle

A senior answer should say performance tuning starts with ST05/SAT evidence, not random code changes.