Databases Reference
In-Depth Information
Performance Tip
For multiuser, multivolume applications, it's possible that billions, or
even trillions, of network packets move between the driver and the data-
base server over the course of a day. Choosing data types that are
processed efficiently can incrementally boost performance.
Using Scrollable Cursors
Scrollable cursors
allow an application to go both forward and backward
through a result set. However, because of limited support for server-side scrol-
lable cursors in many database systems, drivers often emulate scrollable cursors,
storing rows from a scrollable result set in a cache on the machine where the dri-
ver resides (client or application server). Table 2-2 lists five major database sys-
tems and explains their support of server-side scrollable cursors.
Table 2-2 Database Systems Support of Server-Side Scrollable
Cursors
Database System
Explanation
Oracle
No native support of database server-side scrollable cursors.
Drivers expose scrollable cursors to applications by emulating the
functionality on the client.
MySQL
No native support of database server-side scrollable cursors.
Drivers expose scrollable cursors to applications by emulating the
functionality on the client.
Microsoft SQL
Server-side scrollable cursors are supported through stored
Server
procedures. Most drivers expose server-side cursors to applications.
DB2
Native support of some server-side scrollable cursor models. Some
drivers support server-side scrollable cursors for the most recent
DB2 versions. However, most drivers expose scrollable cursors to
applications by emulating the functionality on the client.
Sybase ASE
Native support for server-side scrollable cursors was introduced in
Sybase ASE 15. Versions prior to 15 do not natively support server-
side scrollable cursors. Drivers expose scrollable cursors to applica-
tions by emulating the functionality on the client.
