In high availability environment,deleted events on primary ObjectServer during period of backup ObjectServer down reappear on primary ObjectServer after backup ObjectServer is up
We can recreat the issue using the following steps:
1. Setup standard high availability environment using SQL files shipped with OMNIbus 7.3.1. For how to setup high availability environment, please refer to IBM Tivoli Netcool/OMNIbus 7.3.1 Installation and Deployment Guide.
2. AGG_GATE has the following resync properties:
Gate.Resync.Enable : TRUE
Gate.Resync.Type : 'UPDATE'
Gate.Resync.Master : ''
Gate.Resync.Preferred : ''
3. AGG_B has the following properties:
4. Start AGG_P, AGG_B, AGG_GATE
5. Stop AGG_B, then delete an event in AGG_P
6. Start AGG_B, removed event is back to AGG_P after a while
In above steps, AGG_P is primary ObjectServer, AGG_B is backup ObjectServer, AGG_GATE is bi-directional gateway between them.
In standard high availability environment, resync_old_events trigger is enabled on both ObjectServer by default. This trigger will touch rows in the ObjectServers to ensure repopulation of events in either direction if there are events deleted during the period of any of ObjectServers down.The logic being is that it is better for an event to reappear, than for an event to be lost.In above scenario, the system cannot determine whether the events absence in the primary ObjectServer was due to its intentional deletion or by a replication failure due to the lose of the backup.So after backup ObjectServer is up, the deleted events will appear back in the primary ObjectServer. Though resync triggers can be modified to prevent deleted events appearing again directly after the resync, repopulation of events is the default behavior on a standard high availability environment.Trigger could be modified to do this instead of the repopulation strategy that is the default.
Resolving the problem
Default trigger could be modified/disabled according the system requirement.For how to modify/disable the trigger, please refer to The IBM Tivoli Netcool/OMNIbus 7.3.1 Administration Guide.