A prefix is an optional string that you can specify to be used in creating automatic Snapshot copies. Using prefixes in Snapshot names provides more flexibility than using schedule names in naming automatic Snapshot copies.
Prefix names must be unique within a policy. The length of the prefix cannot exceed the maximum allowable length for Snapshot names; that is, Snapshot names cannot be longer than 255 characters. Prefix names must follow the character encoding rules used by Snapshot names.
If a prefix is specified in the Snapshot schedule, then the schedule name is not used to name Snapshot copies. If the prefix is not specified for a Snapshot schedule within a Snapshot policy, then the schedule name is used.