DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

Recommendation
If you currently do not use array fetch and insert in your CLI applications we recommend that
you start using array operations. There is no default optimal rowset size. The improvement
that can be realized will depend on the number of columns, the size of the row, the network
bandwidth,... As you can conclude from this measurement the larger the rowset the less
significant the improvement. As a rule of thumb we recommend that you experiment with a
rowset size that fits in a 64 KB communication buffer. Note that column-wise binding of the
application array variables is more efficiently supported by the CLI/ODBC Driver than
row-wise binding.
7.3 WebSphere and the DB2 Universal Driver
In this section we discuss the IBM DB2 UDB Universal Driver for SQLJ and JDBC, also known
as the Java Common Connectivity (JCC), from a performance perspective and the DB2
enhancements that will benefit Java in general.
JDBC is a vendor-neutral SQL interface that provides data access to your application through
standardized Java methods.
These methods and interfaces are packaged as DB2 JDBC Drivers and numbered from 1 to
4:
► Type 1
This is the oldest type of driver. It was provided by Sun to promote JDBC when no
database-specific drivers were available. With this driver, the JDBC API calls an ODBC
Driver to access the database. This driver type is commonly referred to as a JDBC-ODBC
bridge driver. Its shortcoming is that ODBC must be implemented and installed on all
clients using this driver type. This restricts it to platforms that have ODBC support, and as
such is mostly Windows centric. Since it also has to translate every JDBC call into an
equivalent ODBC call, the performance of a Type 1 Driver is not great. IBM does not
provide a Type 1 Driver.
This type is no longer commonly used, because virtually every database vendor nowadays
supports JDBC and provides their own (vendor-specific) driver.
► Type 2
A JDBC type 2 Driver relies on platform- and database-specific code to access the
database. The application loads the JDBC Driver and the driver uses platform- and
database-specific code to access DB2. This driver is also known as the “app” driver which
refers to the implementation class name com.ibm.db2.jdbc.app.DB2Driver. This name and
driver class name only applies to the old driver (not the universal) and applies only to DB2
for Multiplatforms. This is the most common driver type used, and offers the best
performance. However, as the driver code is platform-specific, a different version has to be
coded (by the database vendor) for each platform.
The new Universal Driver has a Type 2 implementation available.
► Type 3
With this driver type, also referred to as the “net” driver (implementation class
com.ibm.db2.jdbc.net.DB2Driver), the JDBC API calls are routed through a middleware
product using standard network protocols such as TCP/IP. The driver itself is written in
Java. The middleware translates these calls into database-specific calls to access the
target database and returns data to the calling application. In the case of DB2, this task is
performed by a program called the JDBC applet server. DB2 for z/OS and OS/390 does
not supply a Type 3 Driver. DB2 for Linux, Unix and Windows still has a so-called network
292 DB2 UDB for z/OS Version 8 Performance Topics