Many existing COBOL applications use traditional COBOL data files, such as flat files, VSAM, indexed or sequential files,
etc., to store critical business information. In their day, this type of data storage did the job; however, with the introduction
of relational databases (RDBMSs), the shortcomings of using traditional data storage have come to the forefront. Storing data
in a relational database makes it much easier to customize reports and obtain analytics. Data in an RDBMS is typically easier
to maintain, meaning less down time. In addition, using an RDBMS or data storage is an important step in building scalable
application architectures.
Note: To view a list of supported relational databases, see
Database Management Systems (DBMSs).
Once you have determined that adding a relational database into your application architecture is what you want, your next
step is to consider your deployment options and select one that can best help you to achieve this goal.
Deployment Options
Enterprise Developer provides several solutions that enable you to update a COBOL application to use a relational database:
- Embedded SQL
- In your COBOL programs, you can replace file I/O verbs with embedded SQL (EXEC SQL). The
Enterprise Developer OpenESQL feature enables you to do this. See
OpenESQL for details.
OpenESQL provides the greatest flexibility for RDBMS support from within COBOL applications and is a widely used feature.
However, for existing applications that are currently file based, updating a typical COBOL application to use OpenESQL is
likely to represent a significant effort — potentially many person-years. In this scenario,
Micro Focus provides alternative approaches you can use to achieve the benefits of a relational database in shorter time frames.
- Micro Focus Relativity
- The Relativity product provides an ODBC interface to your COBOL data files. The files essentially become a data source you
can access from any client that uses ODBC or JDBC. This approach enables you to maintain data in COBOL data files without
application change. In addition, you can take advantage of third-party tools, such as Microsoft Office and other software
products, that provide enhanced reporting and analytics by accessing your COBOL data via the ODBC interface. For more information,
see
Micro Focus Relativity Documentation.
- Micro Focus Database File Handler (MFDBFH).
- Using this approach, application code remains unchanged. At run time, existing file I/O statements are translated to automatically
store and retrieve data from your RDBMS instead of data files.
For optimal performance, MFDBH stores COBOL records as a binary BLOB in the RDBMS. To help you with your reporting and analytic
needs, you can optionally create a database view to view the data within the BLOB.
See
Micro Focus Native Database File Handling for details.
Choosing the Best Option
The following provides guidance on how to choose the best deployment option for your COBOL application:
- Data files
- Data files offer the highest performance when accessed locally by the application, but at the cost of reliability and scalability.
Data corruptions can occur due to hardware failure and can result in extended outages while data is recovered. Moving data
remotely or putting in measures to mitigate failure can impact performance.
- Embedded SQL
- Choose embedded SQL if you can reasonably update the application within acceptable time and cost constraints. With any move
from files to RDBMS, expect a loss of performance in the application as data is accessed over a network.
- Relativity
- If your main objective is to simplify access to COBOL application data by third-party applications, Relativity is a good
choice because it requires no change to the application, and data remains within existing files. If you actually need COBOL
data in an RDBMS for other reasons, and you cannot reasonably update the application to use ESQL, consider using either the
MFDBFH or DBC approach.
- MFDBFH
- If you need to move data from files into a database rapidly, MFDBFH offers the best performance. However, this solution does
not allow data to be updated outside of the COBOL program, and it is less flexible with regard to how COBOL fields are mapped
in the table view. If these issues are important, consider using the DBC approach instead.
Performance Considerations
Performance is often the biggest concern when migrating data from files to an RDBMS, and you need to get an idea of the affect
it could have on your application. As each application is different, precise comparisons of performance are not practical.
That said, we recommend that you use these guidelines to help you make a decision:
- Because batch applications are traditionally I/O heavy, migration of data to an RDBMS can have a significant effect on performance.
- Online applications can lose performance in this type of migration, but this loss is minimal and often goes unnoticed by end
users.
- For applications that scale up as the number of users increases, RDBMS performance typically outperforms file access, and
runs even more quickly when accessed over a network or via Fileshare.