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Title
PF (Public Folders) Agents logic when PST size limit is reached -
Description
PF Source Agent logs the following message:
"PM MailKernel::CheckPSTSize Informational 2133 Source agent has stopped processing because the PST file is larger than the allowed limit."
What exactly happens after this message is logged? When the agent is going to return processing where it left off? -
Cause
Upon the agent reaching the PST size limit, it closes the PST and then switches to the next PF Sync root that's part of current collection. If there are no more PF Sync roots (Source PF - Target PF pairs) available in the current PF collection, agent switches to the next PF collection. Please read below for more details.
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Resolution
PF Delta Sync logic explained:
1. PF Source Agent starts and selects PF Sync collection, then the first PF Sync root from that collection.
2. Agent requests all PF changes occurred from the last session from Exchange server. ICS (Incremental Change Synchronization)Exchange mechanism is used which is the same as Exchange relies upon for PF replication. Information about all changed PF items is then recorded into the PF tracking database by their SourceKeys.
3. Agent updates replication streams on all folders under the current PF root.
4. Agent opens tracking database and requests all the PF items from Exchange server by their SourceKeys that were previously recorded in step 2. Agent then copies received PF data into PST file.
5. If PST size limit is reached, agent stops copying process, closes PST and puts it into Transmission queue.
6. Agent then switches to the next PF Sync root thats part of current collection. If there is no more PF Sync roots available in the current PF collection, agent switches to the next PF collection.
7. When working on the next root, agent is following the same logic described in the previous steps.
8. Once agent returns back to original PF root where it was interrupted by reaching PST size limit, it finishes copying remaining PF items by their SourceKeys and re-requests Exchange server to provide new changes.
As seen from above, it becomes obvious that the tracking database (the file is in root of the disk where agent is installed EMWSTP.DAT) plays a key role in the whole synchronization process and loosing this file due to corruption or some other event can result in loss of PF sync changes. In such case Full PF Resync has to be performed.