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

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)


16 January 2015