Each Oracle database includes a set of what is called metadata, or data that describes the structure of the data contained by the database including table definitions and integrity constraints. The tables and views that hold this metadata are referred to as the Oracle data dictionary. All the components discussed in this chapter have corresponding system tables and views in the data dictionary that fully describe the characteristics of the component. You can query these tables and views using standard SQL statements. Table 2-1 shows where you can find some of the information available about each of the components in the data dictionary.
|
Component |
Data dictionary tables and views |
|---|---|
|
Database Shared server |
V$DATABASE, V$VERSION, V$INSTANCE V$QUEUE, V$DISPATCHER, V$SHARED SERVER |
|
Tablespaces |
DBA_TABLESPACES, DBA_DATA_files, DBA_FREE_SPACE |
|
Control files |
V$CONTROLFILE, V$PARAMETER, V$CONTROLFILE_RECORD_SECTION |
|
Datafiles |
V$DATAFILE, V$DATAFILE_HEADER, V$filesTAT, DBA_DATA_files |
|
Segments |
DBA_SEGMENTS |
|
Extents |
DBA_EXTENTS |
|
Redo threads, groups, and numbers |
V$THREAD, V$LOG, V$LOGFILE |
|
Archiving status |
V$DATABASE, V$LOG, V$ARCHIVED_LOG, V$ARCHIVE_DEST |
|
Database instance |
V$INSTANCE, V$PARAMETER, V$SYSTEM_PARAMETER |
|
Memory structure |
V$SGA, V$SGASTAT, V$SGAINFO, V$SGA_DYNAMIC_COMPONENTS, V$SGA_DYNAMIC_FREE_MEMORY, V$SGA_RESIZE_OPS, V$SGA_RESIZE_CURRENT_OPS, V$DB_OBJECT_CACHE, V$SQL, V$SQLTEXT, V$SQLAREA |
|
Work area memory |
V$PGASTAT, V$SYSSTAT, V$SESSTAT |
|
Processes |
V$PROCESS, V$BGPROCESS, V$SESSION, V$LOCK |
|
RMAN recovery |
V$RECOVER_FILE |
|
User passwords |
V$PWFILE_USERS |
The SYSTEM tablespace always contains the data dictionary tables. Data dictionary tables that are preceded by the V$ or GV$ prefixes are dynamic tables, which are continually updated to reflect the current state of the Oracle database. Static data dictionary tables can have a prefix such as DBA_, ALL_, or USER_ to indicate the scope of the objects listed in the view.