Managing Configuration Items › CI Reconciliation › How to Identify and Resolve Ambiguous CIs › CI Ambiguity Example

CI Ambiguity Example

Data from four different data sources is loaded into the CMDB. Each data source uses its own subset of identifying characteristics. Because of this inconsistency, more CIs exist in the CMDB than are desired.

The following are examples of CI ambiguity:

Example: Ambiguous CIs

The following four CIs reside in the CMDB:

• Name(Server1) DNS Name(dns1) Serial Number(serial1)
• Name(Server1) DNS Name(dns1)
• Name(Server2) DNS Name(dns1) Serial Number(serial1)
• Name(Server3) MAC Address(mac1)

Due to shared identifying characteristics, the two instances of Server1 and Server2 are ambiguous with each other. Server3 is not ambiguous.

Every CI has an ambiguity index associated with it. The ambiguity index is approximately the number of existing CIs that match on any of the identifying attributes. The greater the index, the more CIs that match on the identifiers, and therefore the greater the probability that CI data was entered inconsistently and that additional CIs are incorrectly created. CIs with an ambiguity index of zero are unique across all identifiers and are therefore unambiguous.

The ambiguity index of each of the previous CIs is

• First Instance for Server1: Count of other CIs matching name + dnsname + serial number = 1+2+ 1=4
• Second Instance of Server1: Count of other CIs matching name + dnsname = 1+2 = 3
• Server2: Count of other CIs matching name + dnsname + serial number = 0 +2+1 = 3
• Server3; Count of other CIs matching name + mac address = 0+0 = 0