Distributed Relational Database Architecture (DRDA) Protocol

Enhanced Definition

The Distributed Relational Database Architecture (DRDA) is a set of protocols that enables distributed relational database access, allowing applications to access data in remote relational databases from different vendors and platforms. In the mainframe context, DRDA is crucial for z/OS applications (e.g., COBOL, CICS) to interact with DB2 for z/OS or other distributed databases (e.g., DB2 LUW, Oracle via gateways).

Key Characteristics

- Standardized Protocol: DRDA is an open specification managed by The Open Group, promoting interoperability across diverse database systems.
- Client-Server Model: It defines roles such as the Application Requester (AR), which initiates database requests, and the Application Server (AS), which processes those requests. DB2 for z/OS can function as both an AR and an AS.
- Location Transparency: Applications using DRDA do not need to know the physical location or specific platform of the data they are accessing, simplifying development.
- Data Stream Format: DRDA specifies the format of the data streams exchanged between the AR and AS, including SQL statements, data, and metadata.
- Security Features: It supports various security mechanisms, including user ID and password authentication, and can integrate with external security managers like RACF on z/OS.
- Heterogeneous Environment Support: Designed to facilitate communication between different operating systems (z/OS, Linux, Unix, Windows) and various relational database products.

Use Cases

- Accessing Remote DB2 LUW: A CICS transaction or a COBOL batch job running on z/OS querying a DB2 database hosted on a Linux, Unix, or Windows server.
- Application Modernization: Modern distributed applications (e.g., Java, .NET) connecting to and retrieving data from a DB2 for z/OS database using DRDA via DB2 Connect.
- Data Warehousing and ETL: Extracting data from multiple distributed sources into a central data warehouse, potentially located on z/OS, or vice-versa.
- Distributed Transactions: Performing updates across multiple databases (e.g., one on z/OS, another on a distributed platform) within a single logical unit of work.
- Database Federation: A single query issued from a z/OS application that transparently accesses and combines data from several physically distinct databases.

Related Concepts

DRDA is fundamental to the Distributed Data Facility (DDF) of DB2 for z/OS, which enables DB2 to participate in distributed database environments as both a client and a server. It works in conjunction with TCP/IP as the underlying network protocol to transport SQL statements and results between systems. DB2 Connect is an IBM product that acts as a gateway, using DRDA to allow non-z/OS applications to connect to DB2 for z/OS, effectively extending the reach of mainframe data. Applications running under CICS or IMS can leverage DRDA through DB2 for z/OS to access remote data sources.

Best Practices:

Optimize DDF Configuration: Properly configure DB2 for z/OS DDF parameters, including the number of active threads and connection limits, to ensure efficient resource utilization and handle expected workload.
Network Performance Tuning: Ensure robust and high-performance TCP/IP connectivity between DRDA participants, paying attention to network latency and bandwidth, especially for cross-country or cloud connections.
Implement Robust Security: Utilize strong authentication and authorization mechanisms (e.g., RACF for DB2 for z/OS, network security) to protect sensitive data accessed via DRDA.
Monitor DRDA Activity: Regularly monitor DRDA connections, SQL execution, and data transfer using DB2 accounting and statistics traces to identify performance bottlenecks or security anomalies.
Manage Data Conversion: Be aware of the overhead associated with EBCDIC-ASCII character set conversions when exchanging data between z/OS and distributed platforms, and plan accordingly to minimize impact.