Identification rules
The CMDB identification process relies on identification rules to uniquely identify CIs.
An identification rule applies to a CI class and consists of a single CI identifier and one or more identifier entries and related entries, each with a different priority. Each identifier entry defines a unique attribute set with a specific priority and each related entry defines rules for identifying related items. Create strong identification rules that are set with the highest priority for the strongest identifier entries and related entries.
The identification process and identification rules use the CIs attributes for identification:
Unique attributes
Designated sets of criterion attribute values of a CI, that can be used to uniquely identify the CI. Unique attributes can be from the same table or from derived tables.
Required attributes
Designated attributes of a CI that cannot be empty.
Identification rule types
CI dependency is specified in the CI Class Manager by the dependent relationship rules for the CI’s class:
Independent CIs
CIs, such as Server CIs, which exist on their own and are not dependent on any other CIs.
Dependent CIs
CIs depend on a relationship to another CI and can’t exist on their own in the absence of the dependent relationship. For example:
- Network Adapter CIs can’t exist meaningfully without the Hardware CIs that contain them.
- Application CIs can’t exist on their own without the Server CI they are hosted on.
The steps for identifying dependent CIs can be different from the steps for identifying independent CIs. This difference is reflected in the differences between dependent identification rules and independent identification rules:
Independent identification rule
A rule that identifies a CI based on the CI’s own attributes, independently of other CIs or relationships.
Dependent identification rule
A rule in which identifying a CI requires identifying a dependent CI first. A CI can have a dependency on one or more CIs, and a dependent CI can have only a single parent CI with dependency. The relationship types between the CI and its dependent CIs are also included in the identification process. To help with the identification process of dependent CIs, create dependent relationships that define the dependency chain within CI types.
The payload used for the identification of a dependent CI can include a relationship with a qualifier chain. For such a relationship, if there is a matching parent/child pair, the system compares the qualifier chain in the payload, with the qualifier chain of the CIs in the database. If there is a difference, the qualifier chain in the database is updated to match the qualifier chain in the payload for that relationship.
Identifier entries
You can configure an identifier entry to match a CI not only based on the CI’s own attributes (field-based identification) but also based on the CI’s related list (lookup-based identification) such as Serial Numbers or Network Adapters. The lookup table that is used for identification, needs to have a reference field that points to cmdb_ci.
There are three types of identifier entries:
Regular identifier entry
Based on CI’s attributes that uniquely identify the CI.
Lookup identifier entry
Uses a lookup table (related table) which can be any table that has a reference to the CI that is being identified. After you select a related lookup table, you select identifier attributes from the related table that reference either the cmdb_ci table itself, or one of its descendants.
If the lookup records do not already exist, then they are inserted in the lookup table referenced in the identifier entry.
Hybrid identifier entry
A combination of both, a regular identifier entry and a lookup identifier entry.
Example: When discovering virtual machines in a cloud environment which contains two virtual machines with identical serial numbers. A regular identifier entry for the Hardware table such as [Table: Serial Number, Criterion Attributes: Serial Number, Serial Number Type] cannot uniquely identify these two virtual machines. However, a hybrid identifier entry such as [Table: Serial Number, Criterion Attributes: Serial Number, Serial Number Type + (Name field from main Hardware table)] can uniquely identify the two virtual machines.
Guidelines for lookup tables
Follow these guidelines when specifying a lookup table in an identifier entry.
- Ensure that lookup tables reference the cmdb_ci table.
- It is preferable to enforce an exact count match (check box Enforce exact count match (Lookup)) for a stronger identification rule. During lookup identification, this option enforces matching only on exact lookup records count match. See Create or edit a CI identification rule for more details.
- Do not create conflicting identification rules especially for lookup-based rule.
Example: In a CI Identifier for the Hardware class, you specify a lookup-based rule for the Network Adapter class and you also define a CI Identifier for the Network Adapter class. Duplicates might potentially be created in the Network Adapter table, because there are contradicting rules to identify a unique CI in that table:
-
- One rule that looks only at criterion attributes (CI identifier rule)
- Another rule that looks at criterion attributes and referenced sys_id (lookup rule).
Example: CI with related items that needs to be inserted – sysId is available.
var payload = {
items: [{
className:’cmdb_ci_linux_server’,
related: [{
className:’cmdb_ci_spkg’,
values: {
name:’package1′,
version:’version1′
}
}],
values: {
sys_id:’194876usytrr65378098′
}
}]
};
Related entries
You can define related entries which are rules that are based on related CIs. A related entry is based on a related table which can be any table (CMDB or non-CMDB) that has a reference to the CI that is being identified. Related entries let you create or update records on other tables in which the data is associated with the CI being identified by the identifier entries. Related entries are not used to directly identify CIs.
After you select a related table for the rule, the list in Referenced field is populated with fields from the related table that reference either the cmdb_ci table itself, or one of its descendants.
A related entry for a class is derived by child classes for which there no related entries are specified.
Create or edit a CI identification rule
Identification rules are used to uniquely identify CIs in the CMDB, as part of the identification and reconciliation process. Each CMDB class can be associated with a single identification rule.
Create an identification inclusion rule
Narrow the scope of CIs that are included in the identification process by creating an identification inclusion rule.
