Using Scrollable Cursors

Scrollable cursors can move backward and forward in a result set, allowing the application user to scroll back and forth through requested data. SequeLink supports two types of scrollable cursors-static and keyset-driven.

Static and Keyset-Driven Cursors

A static cursor is one that does not detect any changes made to the record after the cursor is opened. For example, if a static cursor fetches a row and another application then updates that row, the values would be unchanged when that row is fetched again. A keyset-driven cursor detects value changes to the record using keys that are saved when the cursor is opened to retrieve the current data values for each row.

Support for the keyset-driven cursors depends on the data store to which you are connecting, as described in Table 2-8.

Table 2-8. Support for Keyset-Driven Cursors (ODBC)  

Database	Conditions for Support
DB2 UDB	The DB2 tables must contain an auto-unique column. The name and other properties of the auto-unique column must be configured in the data source of the SequeLink Server.
Informix	None (inherently supported).
Microsoft SQL Server	The table must contain an identity column.
JDBC Socket	The backend database must support an auto-unique column. The name and other properties of the auto-unique column must be configured in the data source of the SequeLink Server.
ODBC Socket	The backend database must support an auto-unique column. The name and other properties of the auto-unique column must be configured in the data source of the SequeLink Server.
Oracle	None (inherently supported).
Sybase	The table must contain an identity column.

Using Static Scrollable Cursors

The ODBC driver supports static cursors for all types of result set generating statements, including result sets generated by stored procedures.
The ODBC driver supports LOB data for static cursors; however, by default, only the first 4096 bytes of the LOB column is buffered. See the SLKStaticCursorLongColBuffLen connection attribute in Table 1-1 "ODBC Connection Attributes" for more information about specifying the amount of data that is buffered.
To persist a result set as an XML data file with embedded schema, you must use static cursors. See "Persisting a Result Set as an XML Data File" for more information about persisting XML data files.

Using Keyset-Driven Scrollable Cursors

The ODBC driver does not support using keyset-driven cursors on stored procedures or explicit batches.
The ODBC driver cannot use keyset-driven cursors, when the Select statement contains any of the following SQL language constructions:
JOIN
Aggregate functions
GROUP BY
(Informix only). When a fragmented table is not explicitly created with the WITH ROWIDS clause, the ODBC driver returns SQL_SUCCESS_WITH_INFO, with the message that a static cursor was substituted.