Introduction:-
The current topic should be very familiar to the freshers and DBA’S as we know earlier. In general, The data dictionary is structured in tables and views, just like other database data. We must have come across of this. Let us understand with some definitions and commands to get in detailed view.
Definition:- A data dictionary contains: The definitions of all schema objects in the oracle database (tables, views, indexes, clusters, synonyms, sequences, procedures, functions, packages, triggers, and so on).
Why do we need data dictionary views?
The data dictionary is a repository of information about the Oracle database, known as metadata. Metadata is ‘information about information,’ and the data dictionary is information about the database. In this section we want to show you how to use the data dictionary to get information on tables.
Below are some of the Views and Commands detailed for references:
The following data dictionary and dynamic performance views provide useful information about the temporary tablespace of a database.
V$TEMPFILE :- Information about all temp files, lincluding tablespace number of owning tablespace
DBA_TEMP_FILES:- Shows files (temp files) belonging to temporary tablespaces.
DBA_TEM_FREE_SPACE:- Displays the total allocated and free space in each temporary tablespace.
VSTEMP_EXTENT_MAP:- Information for all extents in all locally managed temporary tablespaces.
VSTEMP_SPACE_HEADER:- Shows space used/free for each temp file.
DBA_TABLESPACE_GROUPS:- Displays the tablespace groups and tablespaces that belong to them
The following Views display information about control files
V$DATABASE:- Displays the database information from the control file
V$CONTROLFILE:- lists the names of control files
V$CONTROLFILE_RECORD_SECTION:- Displays the information about the control file record sections
V$PARAMETER:- Displays the names of control files as specified in the CONTROL FILES initialization parameter
The Following views provide information about redo log files
V$LOG:- Displays the redo log file information about the control file
V$LOGFILE:- Identifies redo log groups and members and member status
V$LOG_HISTORY:- Contains the log history information
The following data dictionary views provide information related to Archiving
V$ARCHIVED_LOG :- Displays historical archived log information from the control file
V$ARCHIVED_DEST:- Describes the current instance, all archive destinations, and the current value, mode, and status of these destinations
V$ARCHIVE_PROCESSESS:- Displays information about the state of the various archive rocesses for an instance
V$LOG:- Displays all redo log groups for the database and indicates which need to be archived
Note:-
Altering or manipulating the data in data dictionary tables can permanently and detrimentally affect the operation of a database.
So, Ensure No data in any data dictionary table should be altered or deleted by any user.
