Some important system tables in Oracle:
| 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 |