oracle internal table

internal RDBMS table

X$ : encrypted, sysdba only, fundation of internal mechanism.
example: X$KVIT

Data dictionary(table)

%$ : for storing database structure and definition, created by sql.bsp and $ORACLE_HOME/rdbms/admin
example: OBJ$

static data dictionary(view)

more stable than DD, based on X$% and %$.
A user have different levels of SDD.

type		desc		example
user_%		objects that belong to user own		user_tables
all_%		objects that not belong to user but could access to		all_tables
dba_%		all table, only for sysdba role		dba_users

dynamic performance view(view)

Including and reflect performance of system, dynamic, based on X$%

type		desc		example
GV$%		including all instances		GV$METRIC
V$%		local instance only		V$METRIC

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order of accessing

1. analyse object name
2. the table and view of user own
3. private synonym
4. public synonym
5. throw ORA-00942(cannot find object)