# Embedded-to-dedicated config server transition protocol > Source-anchored research for Embedded-to-dedicated config server transition protocol. Run status: COMPLETED. Parent: [Sharded Cluster Cost Economics](https://llms-explorer.com/tree/sharded-cluster-cost-economics/) · 5 facets · 17 facts · page: https://llms-explorer.com/tree/embedded-to-dedicated-config-server-transition-protocol/ ## How it works - getTransitionToDedicatedConfigServerStatus exposes state, remaining chunk/database/collection counts, jumbo chunks, estimatedRemainingBytes, dbsToMove, and collectionsToMove. Use the database command when automation needs its complete output. (low confidence) — [source](https://www.mongodb.com/docs/manual/reference/command/getTransitionToDedicatedConfigServerStatus.md) - The MongoDB transition tutorial says draining survives cluster restarts because transition status is recorded in config.shards. It also cautions that concurrent collection creation, sharding, or movement can cause interruptions and unexpected results. (low confidence) — [source](https://www.mongodb.com/docs/manual/tutorial/embedded-to-dedicated.md) ## How-to and procedures - Run the staged commands through mongos on the admin database, using db.adminCommand with the command name and numeric value 1. The documented sequence starts draining, polls progress, moves remaining application collections and database primaries, and explicitly commits the transition. (medium confidence) (verified as of 2026-10-14) — [source](https://www.mongodb.com/docs/manual/reference/command/startTransitionToDedicatedConfigServer.md) ## Problems, failure modes and limitations - Operators must manually move unsharded collections with moveCollection, then move database primaries identified by dbsToMove with movePrimary. commitTransitionToDedicatedConfigServer returns an error if a database still uses the config shard as primary or an unsharded collection remains there. (medium confidence) — [source](https://www.mongodb.com/docs/manual/reference/command/startTransitionToDedicatedConfigServer.md) - Atlas describes the transition as online but warns that receiving shards need CPU, memory, and I/O headroom. Atlas cannot scale tier or change storage while the transition plan runs, so capacity must be arranged before starting. These are Atlas operational constraints, not documented guarantees for the self-managed command interface. (low confidence) (verified as of 2026-10-14) — [source](https://www.mongodb.com/docs/atlas/transition-to-dedicated-config-servers.md) - Do not assume that an optimization to skip range deletions is universally available: SERVER-125865 records its revert with fix version 8.3.3, and the replacement SERVER-134413 remains unresolved while explaining that range-deletion waits can delay config-server tier reduction. This is a version-sensitive implementation caveat, not a benchmark of transition cost. (medium confidence) (verified as of 2026-10-26) — [source](https://jira.mongodb.org/browse/SERVER-125865) - Commit explicitly with db.adminCommand({commitTransitionToDedicatedConfigServer: 1}) after evacuation. Commit returns an error if draining is incomplete or a database primary or unsharded collection remains on the config shard. (medium confidence) — [source](https://www.mongodb.com/docs/manual/reference/command/commitTransitionToDedicatedConfigServer.md) ## Comparisons and alternatives - Run db.adminCommand({startTransitionToDedicatedConfigServer: 1}) through mongos to request asynchronous chunk draining. Enable the balancer; a successful start acknowledges the request rather than proving evacuation is complete. (medium confidence) — [source](https://www.mongodb.com/docs/manual/reference/command/startTransitionToDedicatedConfigServer.md) ## Facts and statements - MongoDB 8.3 introduces separate startTransitionToDedicatedConfigServer, getTransitionToDedicatedConfigServerStatus, stopTransitionToDedicatedConfigServer, and commitTransitionToDedicatedConfigServer commands for the embedded-to-dedicated transition. Percona independently describes a parallel granular transition command set in its 8.3 overview. (medium confidence) (verified as of 2026-07-30) — [source](https://www.mongodb.com/docs/manual/reference/command/startTransitionToDedicatedConfigServer.md) - A successful commit removes the config shard from cluster metadata and listShards; the config server continues as a dedicated config server without application shard data. Commit requires draining and manual migrations to have completed. (medium confidence) — [source](https://www.mongodb.com/docs/manual/reference/command/commitTransitionToDedicatedConfigServer.md) - stopTransitionToDedicatedConfigServer stops an in-progress drain and returns the config shard to normal balancing. The documented operation stops the transition; it does not promise to restore the original data placement or undo a completed commit. (low confidence) — [source](https://www.mongodb.com/docs/manual/reference/command/stopTransitionToDedicatedConfigServer.md) - The staged transition commands are documented for self-managed Community and Enterprise deployments and are unsupported in Atlas. Atlas documentation warns against canceling through the UI or reducing shard count during a transition; operators who need cancellation must contact MongoDB Support. (medium confidence) (verified as of 2026-10-14) — [source](https://www.mongodb.com/docs/manual/reference/command/startTransitionToDedicatedConfigServer.md) - The Manning 8.0 chapter describes embedded/dedicated transitions through the older transitionToDedicatedConfigServer and transitionFromDedicatedConfigServer commands. This independently establishes earlier topology support, but does not validate the new 8.3 staged command semantics. (low confidence) — [source](https://www.manning.com/preview/mongodb-in-action-third-edition/chapter-9) - With authorization enabled, startTransitionToDedicatedConfigServer and stopTransitionToDedicatedConfigServer require clusterManager or a role containing the removeShard action. (medium confidence) — [source](https://www.mongodb.com/docs/manual/reference/command/startTransitionToDedicatedConfigServer.md) - The start reference warns against cluster backups while starting the transition, waits for concurrent DDL to finish, and warns that draining can close change-stream cursors that may not be fully resumable. (low confidence) — [source](https://www.mongodb.com/docs/manual/reference/command/startTransitionToDedicatedConfigServer.md) - Manning describes embedded config servers as combining cluster metadata with user data to simplify infrastructure and reduce infrastructure costs. Moving to dedicated config servers therefore changes where application capacity must reside; these sources provide no numeric cost or migration-duration guarantee. (low confidence) — [source](https://www.manning.com/preview/mongodb-in-action-third-edition/chapter-9) - Percona's July 30, 2026 technical-preview announcement explicitly identifies a parallel command set for embedded-to-dedicated config-server transitions. It corroborates the existence of staged control, but does not document each transition command's detailed behavior. (medium confidence) (verified as of 2026-07-30) — [source](https://www.percona.com/blog/percona-server-for-mongodb-8-3-technical-preview-is-now-available/)