2.4Configuration management

"If I make this change, which services will be affected?"—whether a service manager can answer this question accurately depends on whether the elements that make up the service and their relationships are recorded correctly. Configuration management manages the CIs (configuration items) that make up a service and their interrelationships in the CMDB (configuration management database), underpinning change management and release management. This section covers the roles of CIs and the CMDB, linkage with other processes, and the easily confused difference from IT asset management, from the angle of practical judgment.

2.4.1CIs and the CMDB

• A CI (configuration item) is an element that makes up a service and is subject to management. Not only hardware, software, and network equipment but also logical elements such as documents, SLAs, and procedures can be CIs. Each CI has attributes (version, status, owner, etc.) and relationships with other CIs (dependency, composition).
• The CMDB (configuration management database) records and maintains CIs and their interrelationships. If the CMDB is accurate, impact analysis—"which services or business operations does changing a given server affect?"—becomes possible. The CMDB's value lies in its accuracy; a CMDB that has drifted from reality (not kept updated) instead leads to erroneous impact analysis.

2.4.2Linkage with change/release management, and the difference from IT asset management

• Linkage with change and release management: when assessing a change, the CMDB's relationship information is used to analyze the impact scope on CIs (impact analysis); once a change or release is carried out, the CI information in the CMDB (version, status, etc.) is updated to match reality. Configuration management is bidirectionally linked with change and release management, and the CMDB's accuracy is preserved through this linkage.
• The difference from IT asset management: IT asset management aims mainly to grasp asset ownership, quantity, licenses, cost, and lifecycle (from procurement to disposal). Configuration management aims to manage the CIs needed to deliver a service and their interrelationships, emphasizing relationships (dependency structure) and impact analysis. Even for the same equipment, the concern differs between "how many do we own (asset)" and "what does it depend on and how (configuration)."

A service manager is assessing a change to apply an important security patch to the OS of a shared database server. This server may be used by multiple business services, and unless the manager accurately grasps which services the restart accompanying the patch will affect, the availability promised in the SLA could be unintentionally harmed. What the manager relies on here is the CMDB. If the CMDB accurately records each CI (this DB server, the DB instance running on it, the business applications that depend on that DB, and the business services they provide) and their mutual dependencies, then reliable impact analysis—"which business services will this server's restart bring down?"—becomes possible, enabling advance notice to the user departments of affected services, an implementation plan for a low-impact time window, and judgment about the needed standby staffing. Conversely, if past changes have not been reflected in the CMDB and it has drifted from reality, overlooking a dependency leads to an incident where "a service that should not be affected goes down." That is precisely why, once this change is carried out, the CI information in the CMDB (the OS patch level, version, and status) must be reliably updated, keeping configuration management linked with change and release management to maintain the CMDB's accuracy. Note that answering "how many of that server do we own as assets, and how many licenses do we hold" is the concern of IT asset management, whereas the relationship and impact analysis needed here—"what depends on that server, and what does the change ripple out to"—is the concern of configuration management. Because their purposes differ even when the target equipment overlaps, looking only at the asset ledger during impact analysis will not yield the dependencies needed. The value of configuration management thus lies in "keeping accurate CIs and relationships in the CMDB to enable a change's impact analysis," and that accuracy is supported by the linkage of updating with every change and release.

2.4.3Section summary

• A CI (configuration item) is a managed element making up a service; the CMDB records CIs and their interrelationships and supports impact analysis
• Configuration management links with change and release management, updating with every change and release to keep the CMDB accurate
• Configuration management (focused on relationships and impact analysis) differs in purpose from IT asset management, which focuses on grasping ownership, licenses, and cost