JDBC Driver for SQL/MP 3.0

Distributed Transactions

For an application, the NonStop Server for Java JDBC driver supports distributed transactions in a standard way, as

described in the JDBC 3.0 Specification. The JDBC API assumes that distributed transaction boundaries are controlled

either by a middle-tier server or another API, such as the user transaction portion of the Java Transaction API. The

NonStop Server for Java does not support the middleware (those implementing resource managers) pieces of

distributed transactions. Instead, the NonStop Server for Java leaves the implementation of such functionality to the

middleware vendor.

If you are using distributed transactions, you must use the transaction-aware driver, sqlmptx. For more information see

Autocommit Mode and the Transaction Aware Driver, and Nonautocommit Mode and the Transaction-Aware Driver.

Floating Point Support

JDBC/MP driver and NonStop Server for Java use the IEEE floating-point format and SQL/MP stores values in TNS

floating-point format. Therefore, JDBC/MP driver converts any FLOAT (32-bit) number or DOUBLE (64-bit) number

read through SQL/MP to IEEE floating-point format and converts any FLOAT or DOUBLE number to TNS floating-

point format to store in the SQL/MP database.

For a 32-bit floating point number, a TNS floating-point number has a larger exponent than an IEEE floating-point

number. This difference causes the TNS floating-point format being able to represent a larger range of numbers, but

with less precision than the IEEE floating-point format. Converting a TNS 32-bit floating-point number to an IEEE 32-

bit floating-point number has the biggest potential for error.

A TNS 64-bit floating-point number has a smaller exponent than the IEEE floating-point number. This difference

results in the IEEE floating point format being able to represent a larger range of numbers, but with less precision than

the TNS floating-point format.

An exception is thrown anytime one of these conditions occurs when writing data to the database or reading data from

the database:

Overflow

Underflow

Not a Number

Infinity

An SQLWarning can occur indicating a "loss of precision" in the conversion from a TNS floating-point number to an

IEEE floating-point number or from an IEEE floating-point number to a TNS floating-point number.

For the range of floating-point values and double-precision values and considerations for handling them in your

application programs, see the NonStop Server for Java Programmer's Reference.

HP Extensions

All the properties in the basic DataSource implementation are specific to the JDBC/MP driver. For information on

these properties, see Basic DataSource Ojbect Properties.