Below is an alphabetical listing of the Oracle system tables that are commonly used.
System Table Description ALL_ARGUMENTS Arguments in object accessible to the user ALL_CATALOG All tables, views, synonyms, sequences accessible to the user ALL_COL_COMMENTS Comments on columns of accessible tables and views ALL_CONSTRAINTS Constraint definitions on accessible tables ALL_CONS_COLUMNS Information about accessible columns in constraint definitions ALL_DB_LINKS Database links accessible to the user ALL_ERRORS Current errors on stored objects that user is allowed to create ALL_INDEXES Descriptions of indexes on tables accessible to the user ALL_IND_COLUMNS COLUMNs comprising INDEXes on accessible TABLES ALL_LOBS Description of LOBs contained in tables accessible to the user ALL_OBJECTS Objects accessible to the user ALL_OBJECT_TABLES Description of all object tables accessible to the user ALL_SEQUENCES Description of SEQUENCEs accessible to the user ALL_SNAPSHOTS Snapshots the user can access ALL_SOURCE Current source on stored objects that user is allowed to create ALL_SYNONYMS All synonyms accessible to the user ALL_TABLES Description of relational tables accessible to the user ALL_TAB_COLUMNS Columns of user's tables, views and clusters ALL_TAB_COL_STATISTICS Columns of user's tables, views and clusters ALL_TAB_COMMENTS Comments on tables and views accessible to the user ALL_TRIGGERS Triggers accessible to the current user ALL_TRIGGER_COLS Column usage in user's triggers or in triggers on user's tables ALL_TYPES Description of types accessible to the user ALL_UPDATABLE_COLUMNS Description of all updatable columns ALL_USERS Information about all users of the database ALL_VIEWS Description of views accessible to the user DATABASE_COMPATIBLE_LEVEL Database compatible parameter set via init.ora DBA_DB_LINKS All database links in the database DBA_ERRORS Current errors on all stored objects in the database DBA_OBJECTS All objects in the database DBA_ROLES All Roles which exist in the database DBA_ROLE_PRIVS Roles granted to users and roles DBA_SOURCE Source of all stored objects in the database DBA_TABLESPACES Description of all tablespaces DBA_TAB_PRIVS All grants on objects in the database DBA_TRIGGERS All triggers in the database DBA_TS_QUOTAS Tablespace quotas for all users DBA_USERS Information about all users of the database DBA_VIEWS Description of all views in the database DICTIONARY Description of data dictionary tables and views DICT_COLUMNS Description of columns in data dictionary tables and views GLOBAL_NAME global database name NLS_DATABASE_PARAMETERS Permanent NLS parameters of the database NLS_INSTANCE_PARAMETERS NLS parameters of the instance NLS_SESSION_PARAMETERS NLS parameters of the user session PRODUCT_COMPONENT_VERSION version and status information for component products ROLE_TAB_PRIVS Table privileges granted to roles SESSION_PRIVS Privileges which the user currently has set SESSION_ROLES Roles which the user currently has enabled. SYSTEM_PRIVILEGE_MAP Description table for privilege type codes. Maps privilege type numbers to type names TABLE_PRIVILEGES Grants on objects for which the user is the grantor, grantee, owner, or an enabled role or PUBLIC is the grantee TABLE_PRIVILEGE_MAP Description table for privilege (auditing option) type codes. Maps privilege (auditing option) type numbers to type names