CAB vs TCAB
In ITIL/ITSM change management, both relate to reviewing and authorizing changes, but they differ in scope and focus:
CAB (Change Advisory Board) is the standing body that reviews and authorizes normal changes. It’s typically chaired by the Change Manager and includes representatives from across IT (operations, security, architecture, service owners) plus business stakeholders when relevant. Its remit is broad: assessing risk, impact, scheduling, conflicts with other changes, business justification, rollback plans, and post-implementation review. It meets on a regular cadence (often weekly) and handles the full spectrum of change types within its scope.
TCAB (Technical Change Advisory Board), sometimes called Technical CAB or eCAB-technical, is a more narrowly scoped, technically-focused forum. It exists to do the deep technical assessment that a full CAB doesn’t have time or expertise for — peer review of the design, architecture fit, technical risk, dependencies, security/compliance implications at the implementation level, and validation of the artifacts (diagrams, runbooks, rollback procedures). TCAB’s output usually feeds into CAB: a change that has passed TCAB technical review arrives at CAB with the technical risk already vetted, so CAB can focus on business risk, scheduling, and authorization.
A useful way to think about it:
| Dimension | CAB | TCAB |
|---|---|---|
| Primary lens | Business risk, scheduling, authorization | Technical correctness, design quality |
| Participants | Cross-functional (IT + business) | Architects, senior engineers, SMEs |
| Decision | Approve / reject / defer the change | Endorse the technical approach |
| Position in flow | Final gate before implementation | Pre-CAB technical gate |
| Cadence | Regular (e.g. weekly) | As-needed or scheduled per change |
| Artifacts reviewed | RFC, risk assessment, schedule, comms plan | Architecture diagrams, design docs, test/rollback plans |
Worth noting: not every organization runs a separate TCAB. Some fold technical review into CAB itself, others run TCAB only for changes above a certain risk/complexity threshold (which sounds like the model Nikhil is endorsing in your conversation — architect-prepared artifacts before CAB for the larger changes, lighter path for small ones).
Don’t confuse TCAB with ECAB (Emergency CAB) — that’s a separate concept for fast-tracking urgent/emergency changes outside the normal cadence.