alter_snapshot

alter_snapshot 
      ::= 
      "alter" "snapshot" [ schema_name "." ] snapshot_name 
      storage_parameter { storage_parameter } 
      [ "refresh" [ "fast" | "complete" | "force" ] 
      [ "start" "with" date ] 
      [ "next" date ] ] 

[rule list]
This rule is call by

alter_command