Monitoring Opened Cursors by User Session in Oracle Database

List all open oracle cursors by user or username



SQL Code

 1set pages 999 lines 300
 2col username format a40
 3select 	sess.username as username
 4,	sess.sid as sid
 5,	sess.serial# as serial
 6,	stat.value cursors
 7from	v$sesstat stat
 8,	v$statname sn
 9,	v$session sess
10where	sess.username is not null
11and	sess.sid = stat.sid
12and	stat.statistic# = sn.statistic#
13and	sn.name = 'opened cursors current'
14order by value
15/

Sample Oracle Output:

 1USERNAME               SID    SERIAL#    CURSORS
 2--------------- ---------- ---------- ----------
 3SYS                    143         10          1
 4WEBUSER                132      33364          3
 5WEBUSER                116      18996          3
 6WEBUSER                118      23832          3
 7WEBUSER                120        423          3
 8ORA_TIV                126      37072          3
 9WEBUSER                127       4392          3
10WEBUSER                124      20787          4
11SYS                    131      34710          5
12CNUSERMAN              145      19887          5
13CNUSERMAN              129       8407          5
14CNUSERMAN              144      17898          5
15CNUSERMAN              141       3881          5
16ORA_TIV                139       5349          8
17ORA_TIV                115       6676          9
18
1915 rows selected.
20SQL>

Purpose:

  • To identify and display information about user sessions that have opened a significant number of cursors, which can potentially impact database performance and resource utilization.

Breakdown:

Formatting Output:

*   `set pages 999 lines 300`: Adjusts display settings to accommodate potentially large results.
*   `col username format a40`: Formats the `username` column for readability.

Querying Session and Cursor Data:

*   **Joining Views:** Combines information from multiple database views:
    
    *   `v$sesstat`: Contains session-level statistics, including cursor usage.
    *   `v$statname`: Stores names and descriptions of statistics.
    *   `v$session`: Provides details about active user sessions.
    
*   **Filtering Criteria:**
    
    *   `where sess.username is not null`: Includes only sessions with known usernames.
    *   `and sess.sid = stat.sid`: Matches session IDs to ensure accurate cursor data.
    *   `and stat.statistic# = sn.statistic#`: Links statistics to their names.
    *   `and sn.name = 'opened cursors current'`: Focuses on the specific statistic for opened cursors.
    
*   **Selecting Relevant Information:**
    
    *   `select sess.username, sess.sid, sess.serial#, stat.value cursors`: Retrieves username, session ID, serial number, and cursor count for each matching session.
    
*   **Ordering Results:**
    
    *   `order by value`: Presents results in descending order of cursor count, highlighting sessions with the most open cursors.

Key Points:

  • Cursor Focus: Specifically targets the 'opened cursors current' statistic, indicating actively open cursors.
  • Session Identification: Provides details about sessions with high cursor usage, aiding in troubleshooting and optimization.
  • User-Centric View: Presents information in a user-friendly format, allowing for easy identification of sessions contributing to potential cursor issues.

Insights and Explanations:

  • Cursor Management: Oracle uses cursors to manage SQL statement execution. Excessive open cursors can consume memory and resources, potentially impacting performance.

  • Troubleshooting:

    • High cursor counts can signal inefficient application code, unclosed cursors, or database configuration issues.
    • Identifying sessions with high cursor usage directs attention to potential problem areas.
  • Optimization:

    • Reviewing application code for proper cursor handling can help prevent excessive opening.
    • Adjusting database parameters related to cursor management may be necessary in some cases.
  • Monitoring:

    • Regularly monitoring cursor usage can proactively identify and address issues before they impact performance significantly.

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