The CHANGE COLLECTION command modifies a collection by performing
    a change in place. CDO changes the values you specify, and other
    values remain the same.

    Before you can issue the CHANGE COLLECTION command, you must
    issue the RESERVE COLLECTION command to reserve the collection.
    The SHOW COLLECTION or SHOW RESERVATIONS command indicates
    whether a condition is reserved. The RESERVE command creates a
    new version of the element.

    Since a collection is a controlled element, CDO freezes previous
    versions and allows you to modify only the highest visible
    version.