DB2 REXX SQL for VM/ESA^(R): Installation and Reference

Appendix L. Considerations and Restrictions Using the DRDA Protocol

This appendix outlines what you must do to use RXSQL to access a non-DB2 Server for VM application server, and also outlines the restrictions that are specific to using RXSQL in the DRDA protocol. You should also read the appendix in the DB2 Server for VSE & VM SQL Reference manual that discusses the DB2 Server for VM restrictions when using the DRDA protocol.

Publications that contain additional information on Distributed Relational Database and Distributed Data Library can be found in Bibliography.

Using RXSQL in a Distributed Environment

With RXSQL, you can exploit the ability of the DB2 Server for VM application requester to communicate with other application servers that implement the DRDA architecture. The non-DB2 Server for VM application server will receive and process your RXSQL requests and return data to your program.

Prerequisites to Accessing Distributed Data

Software Requirements

DRDA support is available only in the following environments:

• VM/ESA Version 2 Release 1 or later, Licensed Program Number 5684-112

Setup Steps

There are a few setup steps which you must follow before you can use RXSQL to access distributed data.

1. Install RXSQL in Your Distributed Environment

   Before you can use RXSQL to access a non-DB2 Server for VM application server, you should make sure that RXSQL has been installed in your distributed environment. Refer to Chapter 1, Before You Begin for more details.

2. Setup COMDIRs

   A communication directory must be set up specifying the name and address of the application server. The communication directory describes the information pathway between the application requester and the target application server. See the DB2 Server for VM System Administration manual for more details.

3. Issue SQLINIT With Appropriate Protocols

   When invoking SQLINIT, the protocol parameters should be either DRDA or AUTO. When DRDA is specified, the Isolation Level must be CS. Any RXSQL SQLISL commands are ignored and the Isolation Level is fixed as CS. See the DB2 Server for VSE & VM Database Administration manual for more details.

Accessing Distributed Data

To access data in a non-DB2 Server for VM application server you must be connected to that server. You connect to the non-DB2 Server for VM application server when you issue the SQLINIT EXEC, or you can switch application servers while using RXSQL by issuing the CONNECT statement. For the syntax and recommended usage of this statement and other SQL statements used to access data in non-DB2 Server for VM application servers, see the IBM SQL Reference, Version 2, Volume 1 manual. When you are using Extended Dynamic SQL to access a non-DB2 Server for VM application server which does not support Extended Dynamics, such as DB2, then each prepared statement is mapped to either a Static or a Dynamic statement.

Restrictions When Using RXSQL in the DRDA Protocol

DB2 RXSQL has some restrictions in addition to those listed in the appendix "Restrictions with Distributed Relational Database Architecture (DRDA) Protocol" of the DB2 Server for VSE & VM SQL Reference manual.

• Operator commands are not supported when connected to a non-DB2 Server for VM application server. An error condition is returned if you attempt to use them.
• When using Extended Dynamics while accessing a non-DB2 Server for VM application server which maps these statements to Dynamic or Static statements, RXSQL issues an Extended DESCRIBE statements whenever your program issues an OPEN statement. If the prepared insert or select statement is a Static Extended Dynamic statement (for example, it was prepared using a Basic Extended PREPARE or a Single Row Extended PREPARE), then DB2 RXSQL will return an error condition.

  In summary, only Dynamic SQL (regular or Extended Dynamic) is supported when accessing a non-DB2 Server for VM application server that does not support Extended Dynamic SQL.

• When using the Basic Extended PREPARE statement, if the SQL statement being prepared includes parameter markers, you must include the USING attributes_variable clause.
• When using an AS/400* application server and inserting a NULL value for a column, you must use both an indicator_variable and a variable_qualifier for that column. Further, the variable_qualifier must have the correct data type attribute for the column, even when it is a NULL value, to prevent an error condition being returned.

Enhancements When Using RXSQL in DRDA Protocol

You may specify a data type of zoned decimal in a variable_qualifier on data input or output when connected to an application server that supports this data type. Zoned decimal is not valid when connected to an DB2 Server for VM application server.