Goals and directions for a distributed relational database

The third step in your analysis is to assess your short-term and long-term goals.

SQL is the standard IBM^® database language. If your goals and directions include portability or remote data access on unlike systems, you should use distributed relational database on the iSeries™ server.

The distributed database function of distributed unit of work, as well as the additional data copying function provided by DataPropagator™ for iSeries, V8.1, broadens the range of activities you can perform on the iSeries server. However, if your distributed database application requires a function that is not currently available on the iSeries server, other options are available until the function is made available on the operating system. For example, you can do one of the following things:

Provide the needed function yourself.
Stage your plans for distributed relational database to allow for the new function to become available.
Reassess your goals and requirements to see if you can satisfy them with a currently available or announced function. Some alternative solutions are listed in the following table. These alternatives can be used to supplement or replace available function.

Table 1. Alternative solutions to distributed relational database
Solution	Description	Advantages	Disadvantages
Distributed Data Management (DDM)	A function of the operating system that allows an application program or user on one system to use database files stored on a remote system. The system must be connected by a communications network, and the remote system must also use DDM.	For simple read and update accesses, the performance is better than for SQL. Existing applications do not need to be rewritten. Can be used to access S/38, S/36, and CICS^®.	SQL is more efficient for complex functions. Might not be able to access other distributed relational database platforms. Does not perform CCSID and numeric data conversions.
Intersystem Communications Function/Common Programming Interface (ICF/CPI Communications)	ICF is a function of the operating system that allows a program to communicate interactively with another program or system. CPI Communications is a call-level interface that provides a consistent application interface for applications that use program-to-program communications. These interfaces make use of SNA's logical unit (LU) 6.2 architecture to establish a conversation with a program on a remote system, to send and receive data, to exchange control information, to end a conversation, and to notify a partner program of errors.	Allows you to customize your application to meet your needs. Can provide better performance.	Compared to distributed relational database and DDM, a more complicated program is needed to support communications and data conversion requirements.
Display station pass-through	A communications function that allows a user to sign on to one iSeries server from another iSeries server and use that server's programs and data.	Applications and data on remote systems are accessible from local systems. Allows for quick access when data is volatile and a large amount of data on one server is needed by users on several servers.	Response time on screen updates is slower than locally attached devices.

A distributed relational database usually evolves from simple to complex as business needs change and new products are made available. Remember to consider this when analyzing your needs and expectations.