Removing duplicate computer systems from the CMDB

Duplicate computer systems and the components which are related to it, impacts the usability. Use this information to troubleshoot issues related to duplicate computer systems.

To remove duplicate computer systems from the CMDB, perform the following steps:

1. Identify and address duplicate computer systems in source datasets.
2. Identify duplicates in the golden dataset referenced by other applications.
3. Remove duplicates from the golden dataset.
4. Link current discovered hosts to the correct computer system in the golden dataset.

To identify and address duplicate CIs in a source dataset

Check if the computer system exists twice in any source dataset before attempting to resolve duplicates in the target dataset.  There are two causes for duplicate computer systems in a source dataset:

• The discovery product or its integration to CMDB failed to update the computer system to be soft-deleted in the source dataset.
  For example, in BMC Discovery, configure aging limits to ensure non-existant nodes are deleted and configure Continuous Synchronization to ensure the update is passed to CMDB. The discovery product provides updates to the CMDB on changes to the CI, so if the discovery product is retired or no longer scans the computer system without removing it, the data in the source dataset becomes obsolete. 
• The attributes of the computer system changed, and the discovery product discovered it a second time and considers it to be a different computer system.
  Discovery products for servers such as BMC Discovery use different discovery mechanisms than discovery products for workstations such as BMC BladeLogic Automation for Clients.for Clients. Each of them work well with their target application. Investigate the specific computer system, discovery product, and situation which allowed the discovery product to be discovered twice.  In some cases, the discovery product may appear to be a duplicate computer system but actually be a separate one.

The best guideline on resolving duplicates in source datasets is to identify and resolve the issue at the discovery product and push the changes through the integration as normal.  If the computer system does not exist in the discovery product, use the following procedures to remove duplicates in the source dataset as well as the golden dataset.

To identify duplicates in the golden dataset referenced by other applications

The ReconciliationIdentity is used as a unique identifier within several Remedy ITSM suite application features. This related information will be de-linked or lost if the value of ReconciliationIdentity changes. This will happen if either:

• • The ReconciliationIdentity is reset to 0 (zero)
  • The CI is removed from the golden dataset, the source CI is re-identified, and then re-merged into BMC.ASSET.

1. To determine the items related to a CI in Remedy Asset Management, log in to the Asset Console. 
2. Click View.
3. Check the following pages
   • General
   • Specifications
   • Work Info
   • Contracts
   • People
   • Relationships
   • Relationship Details
   • Financials
   • Outages
   • Impacted Areas

Most of this information is stored in ITSM forms and related by the ReconciliationIdentity, so changing the value of ReconciliationIdentity would de-link all of this information.

The computer system created first will have the related information in most cases, both because it has been present longer and also because Asset Management personnel will find duplicate computer systems when trying to relate information to it.  Thus, it is often the case that the computer system which was added last will be the one which should be deleted but the procedure above helps to validate that conclusion.

For more information on queries for identifying duplicate CI's, see Investigating issues with duplicate data in CMDB.

You can use the AR DRIVER utility to execute the queries. This is helpful when automating the process. For more information on using the AR DRIVER utility, see the blog Identifying weak Reconciliation Identification rules with ARDRIVER. 

To delete duplicate computer systems from the golden dataset

After identifying which of the duplicate computer systems will be deleted, and moving over any related information to the computer system which will be retained, use this procedure to delete the duplicates.

1. Set the Cascade Delete option for the two relationship classes. See Common CI and relationship class properties and Relationships represented in a data model diagram.
   • BMC_HostedAccessPoint
   • BMC_HostedSystemComponents.

2. Delete the computer system.

   Deleting the computer system will also delete related hosted system components and IP endpoints. 

3. Update BMC_HostedAccessPoint and BMC_HostedSystemComponents classes to revert changes to the Cascade Delete option.

Alternativevly, instead of updating these relationship class definitions temporarily, you can use the CMDBDRIVER to delete duplicate CI's. Deleting CI's with CMDBDRIVER also removes weak relationships in the process.  For more information on using CMDBDRIVER see the knowledge article, KA369464.

To link current discovered hosts to the correct computer system in the golden dataset

After deleting the duplicate computer system from the golden dataset and from source datasets if necessary, use this process to link the discovered computer system to merge to it:

1. Identify the correct and current computer system in the source dataset by investigating as described above.

2. Reset the Reconciliation Identities of the corresponding computer system in the source dataset.
3. Either manually identify the CI in the source dataset with the one in the golden dataset or run the updated reconciliation job which addresses the issue.