As with user-defined sharding, tablespaces created for directory-based sharding are assigned to chunks.

The total number of chunks is defined by the number of partitions specified in the sharded table. The number of chunks for a given shardspace is the number of partitions assigned to it. The ALTER TABLE ADD, DROP, and SPLIT PARTITION commands on the sharded table increases or decrease the number of chunks.

The GDSCTL SPLIT CHUNK command, which is used to split a chunk in the middle of the hash range for system-managed sharding, is not supported for directory-based sharding. You must use the ALTER TABLE SPLIT PARTITION statement to split a chunk.

Also, just like user-defined sharding, no chunk migration is automatically started when a shard is added to the distributed database. You must run the GDSCTL MOVE CHUNK command for each chunk that needs to be moved to another shard.