Altering the Join Index to a Sparse Map without Specifying the Colocation Option
If you alter the join index to use a sparse map without specifying the COLOCATE USING clause and the join index previously used a sparse map, the colocation name does not change. Otherwise, the colocation name defaults to database_index, where database is the name of the database or user followed by an underscore (_) and index is the name of the join index. If database exceeds 63 characters, database is truncated to 63 characters. If index exceeds 64 characters, index is truncated to 64 characters.
Access Locks during the Alter Join Index Operation
A read lock is placed on the join index during the copy to the new map. The lock is upgraded to an exclusive lock while DBC.TVM is updated and the transaction is committed.
Indexes and the Alter Table Map Operation
Secondary indexes for the table are moved or rebuilt using the new map.
Join indexes on the base table are not moved when the table is moved to a new map. You must use ALTER JOIN INDEX.
System-defined join indexes for the table are moved or rebuilt using the new map.