Performance and Tuning

Improving jConnect performance

There are a number of ways to optimize the performance of an application using jConnect:

Use TextPointer.sendData methods to send text and image data to an Adaptive Server database. See "Updating image data in the database".
Create precompiled PreparedStatement objects for dynamic SQL statements that are used repeatedly during a session. See "Performance tuning for prepared statements in dynamic SQL".
Use batch updates to improve performance by reducing network traffic; specifically, all queries are sent to the server in one group and all responses returned to the client are sent in one group. See "Support for batch updates".
For sessions that are likely to move image data, large row sets, and lengthy text data, use the PACKETSIZE connection property to set the maximum feasible packet size.
For TDS-tunneled HTTP, set the maximum TDS packet size and configure your Web server to support the HTTP1.1 Keep-Alive feature. Also, set the SkipDoneProc servlet argument to "true."
Use protocol cursors, the default setting of the LANGUAGE_CURSOR connection property. See "LANGUAGE_CURSOR connection property" for more information.
If you use TYPE_SCROLL_INSENSITIVE result sets, use them only when the result set is reasonably small. See "Using TYPE_SCROLL_INSENSITIVE result sets in jConnect" for more information.

Additional considerations for improving performance are described in the following sections.

BigDecimal rescaling

The JDBC 1.0 specification requires a scale factor with getBigDecimal. Then, when a BigDecimal object is returned from the server, it must be rescaled using the original scale factor you used with getBigDecimal.

To eliminate the processing time required for rescaling, use the JDBC 2.0 getBigDecimal method, which jConnect implements in the SybResultSet class and does not require a scale value:

public  BigDecimal getBigDecimal(int columnIndex) 
   throws  SQLException

For example:

SybResultSet rs = 
   (SybResultSet)stmt.executeQuery("SELECT 
   numeric_column  from T1");
 while (rs.next())
 {
   BigDecimal  bd rs.getBigDecimal( 
     "numeric_column");
       ...
 }

REPEAT_READ connection property

You can improve performance on retrieving a result set from the database if you set the REPEAT_READ connection property to "false." However, when REPEAT_READ is "false:"

You must read column values in order, according to column index. This is difficult if you want to access columns by name rather than column number.
You cannot read a column value in a row more than once.

SunIoConverter character-set conversion

If you are using multibyte character sets and need to improve driver performance, you can use the SunIoConverter class provided with the jConnect samples. This converter is based on the sun.io classes provided by the Java Software Division of Sun Microsystems, Inc.

The SunIoConverter class is not a pure Java implementation of the character-set converter feature and, therefore, is not integrated with the standard jConnect product. However, Sybase has provided this converter class for your reference, and you can use it with the jConnect driver to improve character-set conversion performance.

Based on Sybase testing, the SunIoConverter class improved performance on all VMs on which it was tested. However, the Java Software Division of Sun Microsystems, Inc. reserves the right to remove or change the sun.io classes with future releases of the JDK. Therefore, this SunIoConverter class may not be compatible with later JDK releases.

To use the SunIoConverter class, you must install the jConnect sample applications. Once the samples are installed, set the CHARSET_CONVERTER_CLASS connection property to reference the SunIoConverter class in the sample2 subdirectory under your jConnect installation directory. See the Sybase jConnect for JDBC Installation Guide for complete instructions on installing jConnect and its components, including the sample applications.

If you are using a database with its default character set as iso_1, or if you are using only the first 7 bits of ASCII, you can gain significant performance benefits by using the TruncationConverter. See "jConnect character-set converters".