[CMDB - Reconciliation or Data Precedence Rules] Understanding the CMDB Reconciliation Rules and troubleshootingIssue This article explains how the CMDB data precedence rules works and what can be checked to troubleshoot.Related LinksHow it Works: In order to control the data sources over the CI data using IRE, OOB we have Reconciliation Definitions/Rules and Data Source Precedence Rules.Each time a CI is inserted or updated the related changes to individual attributes of the CI are registered in cmdb_datasource_last_update with that source name.Check if the data source is allowed to update attributes and if yes it will check if the same attribute is updated by high priority source earlier (by checking the table cmdb_datasource_last_update)If yes, then it will skip those specific attributes (called masking) and continue with the other attributes.Once the update occurs then it will update about these changes in cmdb_datasource_last_update for future runs. CI Insert: When a CI is created through CMDB identification and Reconciliation Engine (CMDB-IRE) then it creates a CI irrespective of the reconciliation rules as its a new CI.And it will create entry in the table Data Source History (cmdb_datasource_last_update) with fields like source, CI, attribute, class. CI Update: When the CI is getting updated via IRE engine then the system will check reconciliation rule if the current data source is allowed to update the attributes/fields of that CI.If the data source is allowed then it will check if the same CI has any history of updates by other high priority data sources before. (It will check the table entries cmdb_datasource_last_update).If the CI attributes are updated by the higher priority data sources previously, then it will skip the update for those attributes. Note: Please note that the data precedence rules are merged with reconciliation rules beginning from Paris. Additional Information: Property glide.reconciliation.override.null (Allow the update of an empty field by a lower priority data source.)