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Need to monitor and manage Oracle database cursors? This guide shows you how to check maximum allowed cursors and track currently open cursors to prevent the dreaded ORA-01000 error.

Understanding Oracle Cursors

Before diving into the queries, let’s understand what cursors are and why monitoring them is crucial for database performance.

What is a Cursor?

In Oracle, a cursor is a memory area that holds the context of a SQL statement execution. Every SQL statement requires a cursor, and Oracle has a limit on how many can be open simultaneously.

Checking Maximum Open Cursors

To find out the maximum number of cursors allowed per session:

SELECT name, value
FROM v$parameter
WHERE name = 'open_cursors';

Monitoring Current Open Cursors

To check how many cursors are currently open in your session:

SELECT a.value, s.username, s.machine
FROM v$sesstat a, v$statname b, v$session s
WHERE a.statistic# = b.statistic#
AND s.sid = a.sid
AND b.name = 'opened cursors current';

Finding Cursor Usage by Session

To get a detailed view of cursor usage by session:

SELECT ss.username,
       ss.machine,
       se.value "Current Cursors"
FROM v$sesstat se,
     v$statname sn,
     v$session ss
WHERE se.statistic# = sn.statistic#
AND ss.sid = se.sid
AND sn.name = 'opened cursors current'
AND ss.username IS NOT NULL
ORDER BY se.value DESC;

Best Practices for Cursor Management

  1. Monitor Regularly: Check cursor usage periodically
  2. Set Appropriate Limits: Configure open_cursors based on application needs
  3. Close Cursors: Ensure applications properly close cursors
  4. Use Cursor Sharing: Enable cursor sharing when appropriate

Troubleshooting ORA-01000 Errors

If you encounter the ORA-01000 “maximum open cursors exceeded” error:

  1. Check current cursor usage
  2. Identify sessions with high cursor counts
  3. Review application code for cursor leaks
  4. Consider increasing open_cursors parameter

Other important parameters affecting cursor behavior:

SELECT name, value
FROM v$parameter
WHERE name IN (
    'session_cached_cursors',
    'cursor_sharing',
    'open_cursors'
);

Resources


This article is part of our Oracle Database Administration series. Check out our other database optimization tutorials.

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