Running Global Projects
Recovery from Reverse Propagation Errors
Recovery from Reverse Propagation Errors
Background - Propagation Process
When the Global Daemon attempts to update a database with another location, it uses two sets of data:
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The required propagation direction ‑ always away from the Primary location of the database
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The detailed information in the database header. This includes:
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Compaction number (Non-additive changes count) NACCNT
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Latest session number
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Claim-list changes count (CLCCNT)
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Header changes count (HCCNT, also known as ELCCNT)
The header information is compared at the two locations to determine what sort of update is required. If the Compaction number is different, then the entire database file must be copied, rather than just sending the required sessions. Otherwise only the required pages in the database are sent.
If the propagation direction which is implied by the Header information at both locations is incorrect, then the Daemon will report errors such as:
Prevented reverse propagation, should be From Remote not Update To
Prevented reverse propagation, should be To Remote not Copy From
The words ‘From’ and ‘To’ indicate the directions implied the Primary location, and that inferred from the database header.
These messages are output as Errors to the daemon window as well as being recorded as Failure in the Transaction database.
The word ‘Copy’ means that the compaction number at the secondary location is higher than that at the primary location; the word ‘Update’ means that the latest session or counters are higher at the secondary location than the primary location. (If neither of the locations is the primary location, then the database at the location nearest to the primary location is the one that is used)
A third message is also possible for another location’s system database where a file is missing:
Missing file. Prevented reverse propagation, should be To Remote not Copy From
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