10 RPGLE Best Practices

If you're an RPG programmer, you should know these 10 best practices. From avoiding common mistakes to taking advantage of built-in features, these tips will help you write better code.

RPGLE (Report Program Generator Language/Extended) is a programming language used to create reports and applications on IBM’s iSeries platform. It is a high-level language that allows developers to quickly and easily create programs that can interact with databases, files, and other programs.

In this article, we will discuss 10 best practices for RPGLE programming that will help you create better programs and improve your development process. We will cover topics such as code readability, error handling, and performance optimization. By following these best practices, you can ensure that your RPGLE programs are robust and reliable.

1. Avoid using the *LIBL and *CURLIB special values

Using *LIBL and *CURLIB can lead to unexpected results, as the library list is dynamic and changes depending on the job. This means that if a program uses *LIBL or *CURLIB, it may not be able to find the object when run in another job with a different library list.

To avoid this issue, hard-code the library name into the source code instead of using *LIBL or *CURLIB. This ensures that the program will always look for the object in the same library regardless of the job’s library list.

2. Pre-allocate files before use

Pre-allocating files before use ensures that the file is available and ready to be used. This eliminates any potential issues with opening a file, such as an error due to the file not being found or already in use by another program. Pre-allocating also allows for better control over the file’s attributes, such as its access mode (read/write), record format, and other settings. To pre-allocate a file, you can use the ALCTL command, which takes parameters such as the file name, access mode, and record format. Once the file has been allocated, it can then be opened using the OPEN command. By pre-allocating files before use, you can ensure that your RPGLE programs are running smoothly and efficiently.

3. Utilize built-in error handling routines

Built-in error handling routines provide a way to catch and handle errors that occur during program execution. This helps ensure the integrity of data, as well as providing an easy way to debug any issues that may arise. The most common built-in error handling routine is the MONITOR group. This allows you to specify which types of errors should be monitored and how they should be handled. For example, if a file read fails, you can use the MONITOR group to display an appropriate message or take other corrective action. Additionally, RPGLE provides several other built-in error handling routines such as ON-ERROR, DOWxx, and CHECKR. These allow you to create more complex error handling logic, such as looping through multiple files until all have been processed successfully. Utilizing these built-in error handling routines makes it easier to write robust code that can handle unexpected errors gracefully.

4. Make sure to close all open files when done with them

Closing files when done with them is important because it frees up resources that can be used by other programs. It also helps to prevent data corruption, as open files are more vulnerable to being overwritten or corrupted. To close a file in RPGLE, the CLOSE operation code should be used. This will ensure that all records have been written and any locks on the file have been released. Additionally, if an error occurs while closing the file, the program will end abnormally so that the issue can be addressed.

5. Utilize free-form RPG for easier readability

Free-form RPG allows for the use of modern coding techniques, such as using meaningful variable names and indentation to make code easier to read. This makes it much simpler to understand what is happening in a program, which can help reduce errors and debugging time. Additionally, free-form RPG eliminates the need for columnar syntax, making programs more concise and efficient. It also supports the use of comments throughout the code, allowing developers to explain their logic and intentions. Finally, free-form RPG enables the use of built-in functions, which can simplify complex calculations and operations. All these features combine to create an overall better programming experience that is both easier to read and maintain.

6. Leverage subprocedures to reduce code duplication

Subprocedures are reusable blocks of code that can be called from multiple places in a program. This allows for the same logic to be used without having to duplicate it, which reduces the amount of code and makes programs easier to maintain. Subprocedures also make debugging simpler since any changes made to them will affect all parts of the program where they are used. To leverage subprocedures, developers should create procedures with parameters that can accept different values each time they are called. This way, the procedure can be reused in various scenarios while still providing the desired results. Additionally, developers should use global variables when needed so that data can be shared between procedures. Finally, developers should ensure that their subprocedures are well-documented so that other developers can easily understand how they work.

7. Take advantage of built-in functions such as %XLATE and %EDITC

%XLATE is a powerful function that allows you to quickly and easily translate data from one character set to another. This can be especially useful when dealing with internationalization, as it allows you to convert text between different languages or dialects without having to write complex code. %EDITC is also very helpful for manipulating strings of characters. It provides an easy way to add, remove, or replace characters in a string, making it much easier to format data correctly. Both functions are incredibly useful for streamlining RPGLE development, and should be taken advantage of whenever possible.

8. Use data structures to pass multiple parameters in a single call

Data structures allow for a more organized and efficient way to pass multiple parameters in a single call. By using data structures, the programmer can group related variables together into one structure, which makes it easier to read and maintain code. Additionally, when passing multiple parameters in a single call, data structures reduce the amount of coding needed by eliminating the need to declare each parameter individually. This also reduces the chances of errors due to typos or incorrect variable names. To use data structures to pass multiple parameters in a single call, the programmer must first define the data structure with all the necessary fields. Then, they must create an instance of the data structure and assign values to its fields. Finally, they must pass the data structure as a parameter to the program being called.

9. Leverage user spaces for temporary storage

User spaces are a type of storage that is allocated in memory and can be used to store data for the duration of an application’s life cycle. This makes them ideal for storing temporary data, such as counters or flags, which need to be accessed quickly and efficiently. User spaces also provide a way to share data between programs without having to use files or database tables. Furthermore, user spaces are not subject to the same locking rules as other objects, so they can be read and written to simultaneously by multiple programs. Finally, user spaces are easy to create and manage, making them a great choice for RPGLE applications. To leverage user spaces, developers should first create a user space object using the CRTUSRSPC command. Then, they can access the user space with the QUSRTVUS API, which allows them to read from and write to the user space.

10. Utilize dynamic SQL instead of static whenever possible

Dynamic SQL allows for more flexibility in the code, as it can be used to create and execute any valid SQL statement at runtime. This means that the same program can be used to access different tables or columns without having to modify the source code. Additionally, dynamic SQL is much easier to maintain than static SQL because changes only need to be made to the SQL statement itself instead of the entire program. Finally, dynamic SQL can also improve performance by allowing the DB2 optimizer to choose the best execution plan based on the current data distribution. To use dynamic SQL in RPGLE, one must first declare a cursor using the DECLARE CURSOR statement. Then, the PREPARE statement is used to prepare the SQL statement from a character variable. After that, the OPEN statement is used to open the cursor and execute the prepared statement. Finally, the FETCH statement is used to retrieve the results from the cursor into host variables.


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