OpenEdge Data Management:<br />Database Administration Automatic extent archiving

Automatic extent archiving is performed by a daemon started by the database broker. The daemon operates in two modes: timed and on-demand. Operating in timed mode, an AI extent switch is performed at the specified interval, in addition to an implicit switch when an extent fills. The minimum time interval is 120 seconds, and the maximum interval is 86400 seconds (24 hours.) Operating in on-demand mode, extents are only switched when they become FULL. In either mode, FULL extents are archived every 5 seconds. When operating the AI File Management Utility daemon, you must have sufficient AI extents to keep at least one extent available for writing at all times.

Timed mode archiving process without Fathom Replication

When the time interval expires for the AI File Management Utility daemon, the following process executes to archive extents:

Awake form 5 second sleep and archive all FULL AI extents.

Check to see if the time interval has expired. If the interval has expired, switch the current extent. Switching causes the current BUSY extent to be marked FULL, and the next EMPTY extent to be marked BUSY.

Mark archived extents as EMPTY.

Sleep for 5 seconds.

It is possible that there will be no FULL extents to archive on many iterations of this loop. After the timer expires, there will be least one FULL extent to archive, the one marked FULL in Step 2. On a busy system, it is possible that additional extents fill during Step 3 and Step 4 of the archiving process. They are archived the next time the daemon awakes.

When you have Fathom Replication enabled on your database, the daemon follows a similar process for archiving extents:

Awake form 5 second sleep and archive all FULL and LOCKED AI extents.

Check to see if the time interval has expired. If the interval has expired, switch the current extent. Switching causes the current BUSY extent to be marked LOCKED, and the next EMPTY extent to be marked BUSY.

Mark archived FULL extents as EMPTY and LOCKED extents as ARCHIVED.

Sleep for 5 seconds.

The difference in the archiving process when Fathom Replication is enabled is that extents cannot be emptied until they have been fully replicated. Extents transition from the BUSY state to the LOCKED state. If a LOCKED extent is replicated before it is archived, it transitions to the FULL state and the AI File Management daemon archives it. If a LOCKED extent is archived before it is replicated, it transitions to an ARCHIVED state, and it becomes the responsibility of Fathom Replication to transition it to an EMPTY state when replicated. Figure 7–2 shows the state transitions graphically.

On-demand archiving process without Fathom Replication

When the AI File Management daemon is operating in on-demand mode, the following process executes to archive extents:

Awake from 5 second sleep. Archive all FULL AI extents, and mark as EMPTY.

Normal database activity causes the current BUSY extent to fill. The extent is marked FULL, and the next EMPTY extent is marked as BUSY.

Sleep for 5 seconds.

On-demand archiving process with Fathom Replication

When the AI File Management daemon is operating in on-demand mode and Fathom Replication is enabled on your database, the following process executes to archive extents:

Awake form 5 second sleep. Archive all FULL and LOCKED AI extents. LOCKED extents are marked as ARCHIVED; FULL extents are marked EMPTY.

Normal database activity causes the current BUSY extent to fill. The extent is marked LOCKED, and the next EMPTY extent is marked as BUSY.

When Fathom Replication has replicated the LOCKED extent, it will mark the extent EMPTY.

Sleep for 5 seconds.