Synon (Cool:2E) / AS400 access path maintenance modes and what the settings *IMMEDIATE, *REBUILD, and *DELAYED mean. These options control how and when the system maintains the index (access path) for a file.

Here’s the breakdown:

🔹 1. *IMMEDIATE (Immediate Maintenance)

• The access path (index) is kept up to date in real-time.

• Every time a record is added, changed, or deleted in the physical file, the system updates the access path right away.

• Pros:

  • Fast retrieval performance (index always current).

• Cons:

  • Higher overhead on each insert/update/delete because index maintenance happens instantly.

🔹 2. *REBUILD (Rebuild on Open)

• The access path is rebuilt only when the file is opened.

• While the file is closed, record changes are not reflected in the access path.

• When the file is opened again, the system reconstructs the index from scratch.

• Pros:

  • Lower overhead during updates to the physical file.

• Cons:

  • Opening the file can be slow, since it must rebuild the access path.

🔹 3. *DELAYED (Deferred Maintenance)

• The access path is not updated immediately, but it is incrementally maintained in the background.

• System updates the index when time permits or during idle I/O cycles.

• If the system ends abnormally or cannot complete, the access path might need to be rebuilt.

• Pros:

  • Good balance between update performance and retrieval performance.

• Cons:

  • Access path might not always be fully up to date.

  • Risk of needing a rebuild if the system crashes.

⚖️ Practical Usage

• *IMMEDIATE: Best for files that are read frequently and need up-to-date access paths (e.g., inquiry screens, reports).

• *REBUILD: Best for files that are updated heavily but opened infrequently with indexed access.

• *DELAYED: Middle ground; reduces update overhead while avoiding full rebuilds every time.

👉 Would you like me to also explain how Synon decides which one to generate (based on file type: arrival sequence, keyed LF, join LF, etc.)? That way, you’ll know when you actually need to override the default.

Got it 👍 — you’re asking about Synon (Cool:2E) / AS400 access path maintenance modes and what the settings *IMMEDIATE, *REBUILD, and *DELAYED mean. These options control how and when the system maintains the index (access path) for a file.

Here’s the breakdown:

🔹 1. *IMMEDIATE (Immediate Maintenance)

• The access path (index) is kept up to date in real-time.

• Every time a record is added, changed, or deleted in the physical file, the system updates the access path right away.

• Pros:

  • Fast retrieval performance (index always current).

• Cons:

  • Higher overhead on each insert/update/delete because index maintenance happens instantly.

🔹 2. *REBUILD (Rebuild on Open)

• The access path is rebuilt only when the file is opened.

• While the file is closed, record changes are not reflected in the access path.

• When the file is opened again, the system reconstructs the index from scratch.

• Pros:

  • Lower overhead during updates to the physical file.

• Cons:

  • Opening the file can be slow, since it must rebuild the access path.

🔹 3. *DELAYED (Deferred Maintenance)

• The access path is not updated immediately, but it is incrementally maintained in the background.

• System updates the index when time permits or during idle I/O cycles.

• If the system ends abnormally or cannot complete, the access path might need to be rebuilt.

• Pros:

  • Good balance between update performance and retrieval performance.

• Cons:

  • Access path might not always be fully up to date.

  • Risk of needing a rebuild if the system crashes.

⚖️ Practical Usage

• *IMMEDIATE: Best for files that are read frequently and need up-to-date access paths (e.g., inquiry screens, reports).

• *REBUILD: Best for files that are updated heavily but opened infrequently with indexed access.

• *DELAYED: Middle ground; reduces update overhead while avoiding full rebuilds every time.