Summary of Oracle common views

Time:2021-5-9

1. Dynamic performance view of database / instance
v$database :displays information about the database from the control file.
V $instance: displays the state of the current instance
V $option: displays Oracle database options and features
        Option must be separately licensed
        whereas features come with the product and are enabled based on
         The product that is running
v$parameter :displays information about the initialization parameter that
           are currently in effect for the session.A new session inherits
           parameter values from the instance-wide values displayed by the
           v$system_parameter view.
v$backup     : Display the backup status of all online data files
v$px_ process_ Sysstat: contains information about the sessions running parallel execution
V $process: displays information about the currently active processes
V $waitstat: displays block content statistics. This table is only updated when timed statistics are enabled
v$system_ Event: total waits for an event
2. View of disk file
v$datafile :datafile information from the control file
V $filestat: displays the number of physical reads and writes done and the total number of single block and multiblock I / OS done at file level
v$log    :displays log file information from the control file
v$log_history :log history information from the control file
v$dbfile :all datafiles making up the database
v$tempfile :tempfile information
V $tempstat: file read / write statistics
v$segment_statistics :segment-level statistics
3. View of content competition
V $lock: lists the locks currently held by the Oracle database and outstanding requests for a lock or latch
V $rollname: lists the names of all online rollback segments
V $rollstat: contains rollback segment statistics
V $waitstat: block content statistics
V $latch: aggregate latch statistics
4. View of memory
v$buffer_ pool_ Statistics: statistics about all buffer pools available for the instance
v$db_ object_ Cache: database objects that are cached in the library cache
V $librarycache: contains statistics about library cache performance and activity
V $rowcache: Statistics for data dictionary activity
v$sysstat:system statistics
v$sgastat :detailed information on the system global area(sga)
5. User / session view
V $lock: lists the locks currently held by the Oracle database and outstanding requests for a lock or latch
v$open_ Cursor: List cursors that each user session currently has opened and parsed, or cached
V $process: displays information about the currently active processes
V $transaction: lists the active transaction in the system
v$px_ Sesstat: parallel execution (PX), contains information about the sessions running
v$px_session :parallel execution(px),contains information about the sessions running
v$sesstat :user session statistics
v$session_ Event: on waits for an event by a session
v$sort_ Usage: it doesn’t seem to be available at 11g
v$sort_ segment:displays information about every sort segment in given instance   Displays the information of each rollback segment given in the instance.
v$session_ Wait: current or last wait for each session
v$session
v$session_object_cache :object cache statistics for the current user session on the local server(instance)
6. Several views related to waiting events:
v$session:   Represents the beginning of a database activity and is regarded as the source.
v$session_ Wait: the view is used to record the waiting status of the active session in real time. It is the current information.
v$session_ wait_ History: Yes, V $session_ Simple enhancement of wait, recording the last 10 waiting times of active session.
V $SQLTEXT: when there is a bottleneck in the database, you can usually start from V $session_ Wait finds the sessions that are waiting for resources. By combining the SID of the session with the view of V $session and V $SQLTEXT, it can capture the SQL statements being executed by these sessions.
v$active_ session_ History: is the core of ash, which is used to record the historical waiting information of the active session. It is sampled once per second. This part of the content is recorded in the memory, and the expected value is to record the content for one hour.
wrh#_ active_ session_ History: it’s V $active_ SESSION_ History is stored in AWR.
v$active_ session_ History: the information in will be refreshed to the load library on a regular basis (once an hour) and reserved for analysis for one week by default.
dba_ hist_ active_ sess_ History: the view is WRH#_ ACTIVE_ SESSION_ History view and several other views are jointly presented, and historical data is usually accessed through this view.
v$system_ Since V $session records dynamic information and is related to the life cycle of session, but does not record historical information, Oracle provides the view v $system_ Event to record the summary information of all waiting events since the database was started. Through this view, users can quickly get the general situation of database operation.

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