Oracle data dictionaries

System Table Name	Brief Description	Related Views
SYS.OBJ$	Contains information about all database objects	USER_OBJECTS, ALL_OBJECTS, DBA_OBJECTS
SYS.TAB$	Stores information about tables and clusters	USER_TABLES, ALL_TABLES, DBA_TABLES
SYS.COL$	Contains column definitions for tables and views	USER_TAB_COLUMNS, ALL_TAB_COLUMNS, DBA_TAB_COLUMNS
SYS.USER$	Stores information about database users	USER_USERS, ALL_USERS, DBA_USERS
SYS.IND$	Contains information about indexes	USER_INDEXES, ALL_INDEXES, DBA_INDEXES
SYS.SEQ$	Stores information about sequences	USER_SEQUENCES, ALL_SEQUENCES, DBA_SEQUENCES
SYS.CDEF$	Contains information about constraints	USER_CONSTRAINTS, ALL_CONSTRAINTS, DBA_CONSTRAINTS
SYS.TS$	Stores information about tablespaces	USER_TABLESPACES, DBA_TABLESPACES
SYS.FET$	Contains information about features and options	V$FEATURE_USAGE_STATISTICS
SYS.SOURCE$	Stores source code for PL/SQL objects	USER_SOURCE, ALL_SOURCE, DBA_SOURCE
SYS.TABCOMPART$	Stores information about table partitions	USER_TAB_PARTITIONS, ALL_TAB_PARTITIONS, DBA_TAB_PARTITIONS
SYS.IMSVC$	Contains information about Instance Management Services	V$SERVICES
SYS.PARTOBJ$	Holds information about partitioned objects	USER_PART_TABLES, ALL_PART_TABLES, DBA_PART_TABLES
SYS.ATTRCOL$	Stores information about attribute columns for object tables	USER_TYPE_ATTRS, ALL_TYPE_ATTRS, DBA_TYPE_ATTRS
SYS.FILE$	Contains information about datafiles and tempfiles	DBA_DATA_FILES, DBA_TEMP_FILES
SYS.TRIGGER$	Stores information about database triggers	USER_TRIGGERS, ALL_TRIGGERS, DBA_TRIGGERS
SYS.SEG$	Stores segment header information	USER_SEGMENTS, DBA_SEGMENTS
SYS.UNDO$	Contains information about undo segments	DBA_UNDO_EXTENTS
SYS.JOB$	Holds information about scheduled jobs (deprecated)	USER_JOBS, DBA_JOBS
SYS.AUDIT$	Stores audit trail information	DBA_AUDIT_TRAIL
SYS.LOB$	Stores information about LOB columns	USER_LOBS, ALL_LOBS, DBA_LOBS
SYS.CONTEXT$	Contains information about context namespaces	ALL_CONTEXT
SYS.RECYCLEBIN$	Holds information about objects in the recycle bin	USER_RECYCLEBIN, DBA_RECYCLEBIN
SYS.SCHEDULER$_JOB	Stores information about Oracle Scheduler jobs	USER_SCHEDULER_JOBS, DBA_SCHEDULER_JOBS
SYS.DEPENDENCY$	Stores object dependencies	USER_DEPENDENCIES, ALL_DEPENDENCIES, DBA_DEPENDENCIES