3GPP 21.900 v20.0.0 — the document's own text

4.10.2 Mirror Change Requests

Taught in 3. What a Release is, and what freezing one costs (How standards actually get made, in depth), 5. The Change Request, field by field (How standards actually get made, in depth), 4. The change request and the release (How standards actually get made, overview), 3. One idea, from proposal to published text (How standards actually get made, quick start).

When a Group produces a Change Request changing an early Release of a specification, it shall check whether the same change also needs to be made to later Releases of the specification. Changes which are corrective or clarifying in nature will generally be applicable to such other versions.

Where it is determined that several Releases are affected, an (independently numbered) Change Request shall be created for each such affected version of the specification. Such CRs are termed "mirror Change Requests". The principal CR and its related mirror CRs should be grouped together for the purpose of presentation to the TSG (unless some other grouping is more logical).

The TSG shall approve (or postpone or reject) a CR to a given Release together with the corresponding mirror CRs to later Releases. This will provide consistency between Releases.