USER_TAB_COMMENTS Stores comment information on tables.

USER_COL_COMMENTS Stores comment information for columns.

USER_CONSTRAINTS CONTRAINT_TYPE column will list the first character of the first word that best describes each type of constraint.

ALL_CONSTRAINTS CONTRAINT_TYPE column will list the first character of the first word that best describes each type of constraint.

USER_OBJECTS Can be used to verify the validity status of all user database objects.

ALL_OBJECTS Can be used to verify the validity status of all database objects.

USER_UPDATABLE_COLUMNS COLUMN_NAME and UPDATABLE will tell you whether the columns in a complex view can be modified.

USER_INDEXES Contains the name of the index and it uniqueness.

USER_IND_COLUMNS Contains the index name, the table name, and the column name.

USER_SYS_PRIVS Shows all privileges associated with this user.

SESSION_PRIVS Shows all privileges available in this session.

USER_ROLE_PRIVS Identifies the roles granted to you.

ROLE_ROLE_PRIVS Identifies the roles granted to other roles in the database.

ROLE_TAB_PRIVS Identifies object privileges granted to roles.

ROLE_SYS_PRIVS Identifies system privileges granted to roles.

SESSION_ROLES Identifies roles available to the current session.