Oracle Data Dictionary: $ v _

In addition to the preceding view, Oracle also has a set of virtual tables used to record the current database activity. As the name suggests, dynamic performance tables are not real tables. Therefore, not all users can access these tables. However, the database administrator is allowed to query and create views of these tables. The administrator can also grant other users the permission to access these views.

SYS users have dynamic performance tables and all table names starting with V _ $. A view is created for these tables, while a synonym is created for the view. The synonym name starts with "V $.

Display the status, Logon Time, and user name of the V $ SESSION View:

1. SQL>SELECTStatus, logon_time, sid, usernameFromV $ session;

Displays information about each log group:

1. SQL>SELECT*FromV $ LOG;

Display the database ID, database name, and log mode in the V $ DATABSE View:

1. SQL>SELECTDbid,Name, Created, log_modeFromV $Database;

You can use the following code to query information about a dictionary table:

1. SQL>SELECTCommentsFromDictionary table_name ='Dictionary'/

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The data dictionary mainly provides all information in the database. Therefore, it can be used to view the required data through various views. The read-only format of the data dictionary prevents any user from editing or modifying it.