Distributed relational database function and SQL
A distributed relational database consists of a set of SQL objects that are spread across interconnected computer systems.
These relational databases can be of the same type (for example, DB2® UDB for iSeries™) or of different types (DB2 Universal Database™ for z/OS®, DB2 for VSE and VM, DB2 Universal Database (UDB), or non-IBM database management systems which support DRDA®). Each relational database has a relational database manager to manage the tables in its environment. The database managers communicate and cooperate with each other in a way that allows a given database manager access to run SQL statements on a relational database on another system.
The application requester supports the application side of a connection. The application server is the local or remote database to which an application requester is connected. DB2 UDB for iSeries provides support for Distributed Relational Database Architecture™ (DRDA) to allow an application requester to communicate with application servers. In addition, DB2 UDB for iSeries can call exit programs to allow access to data on other database management systems which do not support DRDA. These exit programs are called application requester driver (ARD) programs.
DB2 UDB for iSeries supports two levels of distributed relational database:
- Remote unit of work (RUW)
Remote unit of work is where the preparation and running of SQL statements occurs at only one application server during a unit of work. DB2 UDB for iSeries supports RUW over either APPC or TCP/IP.
- Distributed unit of work (DUW)
Distributed unit of work is where the preparation and running of SQL statements can occur at multiple applications servers during a unit of work. However, a single SQL statement can only refer to objects located at a single application server. DB2 UDB for iSeries supports DUW over APPC and, beginning in V5R1, introduced support for DUW over TCP/IP.
- DB2 UDB for iSeries distributed relational database support
The IBM® DB2 Query Manager and SQL Development Kit for iSeries licensed program supports interactive access to distributed databases.
- DB2 UDB for iSeries distributed relational database example program
A remote unit of work relational database example program is included with the SQL product. Several files and members within the QSQL library can help you set up an environment that runs a distributed DB2 UDB for iSeries example program.
- SQL package support
The i5/OS® operating system supports SQL packages. The object type is *SQLPKG.
- CCSID considerations for SQL
If you are running a distributed application and one of your systems is not a System i™ product, the server on the System i platform cannot have the job coded character set identifier (CCSID) value set to 65535.
- Connection management and activation groups
SQL connections are managed at the activation group level. Each activation group within a job manages its own connections and these connections are not shared across activation groups.
- Distributed support
DB2 UDB for iSeries supports these levels of distributed relational database.
- Distributed unit of work
Distributed unit of work (DUW) allows access to multiple application servers within the same unit of work.
- Application requester driver programs
To complement database access provided by products that implement Distributed Relational Database Architecture (DRDA), DB2 UDB for iSeries provides an interface for writing exit programs on a DB2 UDB for iSeries application requester to process SQL requests. Such an exit program is called an application requester driver (ARD).
- Problem handling
The primary strategy for capturing and reporting error information for the distributed database function is called first failure data capture (FFDC).
- DRDA stored procedure considerations
The i5/OS Distributed Relational Database Architecture (DRDA) server supports the return of one or more result sets in a stored procedure.
Parent topic:
SQL programming
Related concepts
Introduction to DB2 UDB for iSeries Structured Query Language
SQL packages
Distributed database programming
Related reference
Accessing data using Distributed Relational Database Architecture (DRDA)