The PARTITION command defines a collection of sessions used to transfer SQL requests to the database. A DML command may name the partition to be used for its requests to the database.
A default session partition may still be created using the SESSIONS and PACK parameters of the BEGIN LOAD command.
This command works in conjunction with a DML parameter, PARTITION, which names the session partition that a DML’s SQL will use. If the DML command does not have a PARTITION parameter, then the default partition created using the SESSIONS and PACK parameters of the BEGIN LOAD command will be used.