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ST04: Monitor Database Performance

Updated Dec 20, 2023

What is T-code ST04?

ST04 is utilized for monitoring database performance, providing comprehensive historical data and statistics for evaluating database performance. This facilitates the identification of improvement opportunities from both an application and system perspective.

Key Performance Metrics:

  1. Data Buffer Cache:

    • Maintain a size & quality above 95% to minimize physical reads from the disk.
  2. User/Recursive Call:

    • Ensure a ratio greater than 2, as recursive calls tend to increase over time.
  3. Read/User Call:

    • Keep the ratio below 30, as a higher value indicates expensive SQL statements.
  4. Time/User Call:

    • Maintain the time per user call below 15ms for optimal performance.
  5. Busy Time & CPU Time Ratio:

    • Aim for a 60:40 ratio; a higher ratio suggests the need for tuning.
  6. Sort Sections:

    • Limit to less than 0.1% of total sorts.
  7. Shared Pool Statistics:

    • Ensure DD (Data Dictionary) cache quality and SQL area get ratio are both above 99%.
  8. Instance Performance:

    • Aim for a Soft Parse Ratio as close to 1 as possible for better system performance. Consider a similar approach for the in-memory sort ratio.

ST04 Database Performance Overview:

  • Data Buffer:
    • Memory area storing database data/blocks for faster access.
    • Quality (Hit Ratio): Frequency of finding requested data in memory without disk access.
    • Reads: Sum of disk and memory access since the start of the database server.
    • Buffer Busy Wait: Indicates contention when a session cannot access a database block due to buffer busyness.