Catalog Store Cursor Sensitivity

SAP Sybase IQ cursors are classified by their sensitivity to changes in the underlying data. In other words, cursor sensitivity is defined by the changes that are visible.

• Insensitive cursors – The result set is fixed when the cursor is opened. No changes to the underlying data are visible.
• Sensitive cursors – The result set can change after the cursor is opened. All changes to the underlying data are visible.
• Asensitive cursors – Changes may be reflected in the membership, order, or values of the result set seen through the cursor, or may not be reflected at all.
• Value-sensitive cursors – Changes to the order or values of the underlying data are visible. The membership of the result set is fixed when the cursor is opened.

The differing requirements on cursors place different constraints on execution and therefore affect performance.

• Cursor sensitivity example: A deleted row
  This example uses a simple query to illustrate how different cursors respond to a row in the result set being deleted.
• Cursor sensitivity example: An updated row
  This example uses a simple query to illustrate how different cursor types respond to a row in the result set being updated in such a way that the order of the result set is changed.