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BMC Discovery 11.1
BMC Discovery 11.1 and above
External manipulation of Discovery data in the CMDB, or network errors during creation of data, may cause data in the CMDB to be out of sync with Discovery, leading to errors during sync.
Discovery Shadow Copy has some transient incorrect information which it will automatically correct
In all versions of BMC Discovery, a Resync may correct any discrepancies.
But, in 11.1 and later versions, you do not need a Resync to correct many of these problems.
Version 11.1 and later will automatically correct a number of out-of-sync conditions (see examples below) without the need for a resync.
Instance missing on delete
Example: Failed deletion of BMC_Dependency BMC_SoftwareServer:software_server_name on HostA - BMC_ComputerSystem:HostA : Instance not found (120006)
In this case, Discovery tries to delete a CI or relationship, and the CMDB says it doesn't exist. Discovery will now update the Shadow Copy so that Discovery knows that the CI or Relationship does not exist. Since Discovery was trying to delete it, and it does not exist, then there is not actually a problem. But, on subsequent Sync activities, Discovery should stop trying to delete the CI or Relationship.
Instance missing on update
Example: ARERR ERROR (120006): Instance not found
In this case, Discovery tries to update a CI or Relationship and the CMDB says it doesn't exist. Discovery will now delete the Shadow Copy of this CI or Relationship, and the next time this is sync'd, Discovery knows it doesn't exist and creates it.
Relationship endpoints missing or marked as deleted
Example: ARERR 120141: Cannot set MarkAsDeleted to "No" on the relationship instance because one or both of the relationship endpoints are MarkAsDeleted
Discovery tries to create a relationship and the CMDB says that one of the endpoints is either marked as deleted or doesn't exist at all. Discovery will now note the state of the endpoints and update the Shadow Copy to match that, so that on the next sync it knows the correct action to take.
Failure during create
If Discovery is trying to to create a CI or relationship, and it gets an error (i.e. a timeout), it doesn't know if the CMDB actually created it. In 10.2 and 11.0 it was assumed that the CI was not created and Discovery would try again the next time, but if it had been created, this would cause a duplicate. Now, if a create gets an error, Discovery notes that, and the next time, it will ask the CMDB if the CI actually exists.
In all of these cases, Discovery sorts itself out internally (i.e. the shadow copy and CMDB are back in sync), but it may require another sync of the devices (not a Resync) to be up to date.
Note about Resync:
Repeated Resync's sometimes continue to show errors such as 120141 even though the Resync finished successfully.
The solution in 11.1 and later is to stop performing Resync.
Instead, after the Resync, sync again the Hosts/Devices that are mentioned in the error messages. Or, sync again the entire estate.
The messages should go away.