Oracle provides dynamically populated performance tables, owned by SYS, that permit the DBA to view current information about a wide variety of conditions in the database. These tables are generally accessed via their public synonyms. In all cases except V$OBJECT_USAGE, where the two names are identical, the table name is the same as the synonym name, except for the insertion of an underscore character before the dollar sign. An example would be the public synonym of V$SQLXS for the table SYS.V_$SQLXS. Table 3-2 is a complete list of these synonyms, and Table 3-3 expands that list to show the columns in each of the underlying Views.