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
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