• Clients that run IMS have exceeded a workload of 100 million transactions daily.
So what’s the truth regarding the need to change? Are legacy systems obsolete, or should they endure as long as they’re effective? Steve Tockey, author of Return on Software (2003), states that after a certain time, legacy systems become too costly to keep. This is primarily due to additional requirements that the legacy system can’t perform, or a lack of capacity. However, is there a type of middleware that can extend the life of legacy systems?
Some might consider using an SQL-Based Middleware (SBM) approach. SBM’s main function is providing realtime SQL data access to legacy data. This lets newer technology (Internet/ Java/Windows) applications access legacy data as if it were any other type of contemporary database. This might preclude the need to do a costly migration from IMS to Oracle. In today’s economy, SBM might make sense.
SBM is a client/server middleware software solution providing real-time access to legacy data. For example, an Internet or desktop application issues a request to the SBM. The result would be a database action, or data returned to the calling application. Characteristics of an SBM include:
• Data dictionary that stores the data layout for supported data sources.
• SQL data access to supported data sources
• Support for standards such as Open Database Connectivity (ODBC), Object Linking and Embedding Database (OLEDB), Java Database Connectivity (JDBC), SQL, and Microsoft .NET.
The architecture is straightforward. The two main pieces (client and server) exchange messages in response to an SQL request by a client application. The server issues native calls to the legacy or other data sources. If the data source is a relational database, the message sent to it will be in SQL; otherwise, it’s sent in a native format. Figure 1 shows the data flow that occurs after an SQL request.