The V$SESSION view presents session information in the current database.
Overview
The V$SESSION view is a dynamic performance view in PolarDB for PostgreSQL (Compatible with Oracle). It presents session information in the current database. A session is the connection between a user and the database. Each time when a user logs on to a database, a new session is created. The V$SESSION view can be used to diagnose session-level problems and query the users connected to the database and their activities.
Each row in the V$SESSION view represents a session that is active or recyclable. The following table describes some of the most commonly used columns in this view:
Column | Type | Description |
SID | numeric | Session identifier. |
SERIAL# | oid | Serial number of the session. Similar to SID, it uniquely identifies the session. |
USERNAME | character varying (128) | Name of the user in the session. |
USER# | oid | Internal identifier of the user. |
STATUS | character varying (8) | Status of the session, such as ACTIVE, INACTIVE, and KILLED. |
SERVER | character varying (9) | Server type, such as DEDICATED (the session is connected through a dedicated server) or SHARED (the session is connected through a shared server). |
MACHINE | text | Name of the client machine. |
PROGRAM | character varying (30) | Name of the program that started the session. |
TYPE | text | Session type, such as USER (which indicates a user session) and BACKGROUND (which indicates a background process session). |
SQL_ID | character varying (13) | ID of the SQL statement that is being executed. |
LAST_CALL_ET | numeric | The elapsed time (in seconds) since the last calling. |
LOGON_TIME | timestamp with time zone | Time of logon. |
BLOCKING_SESSION_STATUS | text | Status on whether the session is blocked. |
EVENT | text | The event in a wait or most recently waited. |
This view is an important tool used by database administrators (DBAs) to monitor, diagnose, and optimize database performance. For example, the DBA can query the V$SESSION view to identify slow sessions, analyze row lock contention, or determine which sessions are consuming the most resources.