Distributed Relational Database - DRDA protocol

Enhanced Definition

DRDA (Distributed Relational Database Architecture) is a set of open protocols that enables applications to access relational databases located on different systems, potentially from different vendors, in a distributed environment. It defines how distributed database requests are exchanged between an application requester (client) and a database server (application server), facilitating seamless data access across a network. In the z/OS context, DRDA is crucial for connecting DB2 for z/OS databases with other DB2 instances or non-DB2 databases.

Key Characteristics

- Standard Protocol: DRDA is an open, published architecture, allowing interoperability between various relational database management systems (RDBMS) that support it, including IBM DB2 family (z/OS, LUW), and other vendors via gateways.
- Client-Server Architecture: It defines roles for an Application Requester (AR) (client) and an Application Server (AS) (server), where the AR sends SQL requests and the AS processes them and returns results.
- Location Transparency: Applications can access data without needing to know the physical location of the database, as long as the connection is configured, simplifying application development.
- Distributed Unit of Work: Supports various levels of distributed units of work, from single-site updates to multi-site updates with two-phase commit protocols for maintaining data integrity across multiple databases.
- Data Stream Format: Specifies the format of the data stream exchanged between AR and AS, including SQL statements, data values, and control information, ensuring consistent communication.
- Security Features: Includes mechanisms for authentication (e.g., user ID and password) and authorization to secure distributed database access and protect sensitive data.

Use Cases

- Connecting z/OS DB2 to Distributed Platforms: Enabling applications running on Windows, Linux, or AIX (e.g., using DB2 LUW, Java applications, .NET applications) to access data stored in DB2 for z/OS databases.
- Distributed Query Processing: Allowing a single SQL query to retrieve data from multiple DB2 for z/OS subsystems or from a DB2 for z/OS subsystem and another DRDA-compliant database on a different platform.
- Data Replication and Synchronization: Facilitating tools and processes that replicate data between DB2 for z/OS and other distributed databases for reporting, disaster recovery, or data warehousing purposes.
- Application Modernization: Integrating legacy mainframe data with modern distributed applications, enabling new user interfaces or services to leverage existing mission-critical data securely.

Related Concepts

DRDA is fundamental to DB2 Connect on distributed platforms, which acts as a gateway or client to access DB2 for z/OS databases. It works in conjunction with TCP/IP as the underlying network protocol, enabling communication between disparate systems. Within DB2 for z/OS, DRDA is managed by the Distributed Data Facility (DDF), which handles incoming and outgoing distributed requests, making the z/OS database accessible to remote clients and allowing z/OS applications to access remote databases.

Best Practices:

Secure DDF Access: Configure DB2 DDF (Distributed Data Facility) with appropriate RACF or external security manager rules to control which users and applications can access the z/OS database remotely.
Optimize Network Configuration: Ensure efficient TCP/IP network configuration between the Application Requester and DB2 for z/OS to minimize latency and maximize throughput for distributed queries.
Use Connection Pooling: For distributed applications, implement connection pooling to reduce the overhead of establishing new DRDA connections for each transaction, improving application performance.
Monitor DDF Activity: Regularly monitor DB2 DDF activity using DB2 accounting and statistics traces to identify performance bottlenecks, high-volume users, or potential security issues.
Plan for Two-Phase Commit: When performing distributed updates across multiple DRDA -compliant databases, ensure proper configuration and monitoring of two-phase commit protocols to maintain data integrity and recoverability.