The catalog commands are:

• createCollection (create collection or view)
• renameCollection
• shardCollection
• dropCollection
• collMod (change collection options)
• createIndexes
• dropIndexes

Routing changes:
An explicit createCollection, renameCollection, and dropCollection will always be routed to the config server, since they now always modify the sharding catalog.

collMod, createIndexes, and dropIndexes will have a unified code path between sharded and unsharded collections: they will always be sent to the primary shard (with a database version) plus all shards that own chunks for the collection (with shardVersions).

dropCollection will also have a unified code path between sharded and unsharded, but it will still be broadcast to all shards (since we do not delete catalog data from a donor shard after moving the last chunk off the donor, and we now allow moving unsharded collections).