How does RPG handle file handling and database access? Explain the techniques and commands involved.

RPG (Report Program Generator) provides comprehensive support for file handling and database access. It offers techniques and commands that enable developers to interact with files and databases efficiently. Let's explore how RPG handles file handling and database access:

File Handling:
RPG provides several file handling techniques that allow reading, writing, updating, and deleting records in both physical and logical files. The key concepts and commands involved in file handling are:

1. File Specifications:
RPG programs start with file specifications that define the files being used and their characteristics. The file specifications specify the file layout, organization, access method, record format, and other relevant attributes.
2. Input and Output Operations:
RPG supports various input and output operations for file handling:

* READ: The READ operation retrieves a record from a file into specified data fields in the program.
* WRITE: The WRITE operation adds a new record to a file or updates an existing record.
* UPDATE: The UPDATE operation modifies an existing record in a file.
* DELETE: The DELETE operation removes a record from a file.
3. File-Level Keywords (FLKs):
RPG utilizes File-Level Keywords (FLKs) to define file operations. FLKs provide control and functionality during file processing. Examples of FLKs include Chain (CHAIN), Setll (SETLL), Setgt (SETGT), Reade (READE), Readp (READP), and More (MORE).
4. Data Structures and Record-Level Access:
RPG supports data structures that allow grouping related fields together. These data structures can represent entire records, making it easy to access and manipulate multiple fields simultaneously.

Database Access:
RPG also provides features for accessing databases, such as IBM Db2 for IBM i. It allows developers to interact with the database using SQL statements and built-in functions. The techniques and commands involved in database access are:

1. SQL Statements:
RPG supports embedded SQL, which allows developers to include SQL statements within their RPG programs. This enables interaction with the database, including querying, updating, and manipulating data. SQL statements in RPG are enclosed within EXEC SQL and ENDEXEC keywords.
2. SQL Cursors:
RPG uses SQL cursors to fetch data from a result set returned by a SELECT statement. Cursors provide control over the result set and allow sequential processing of the retrieved data.
3. Embedded SQL Variables:
RPG allows the declaration of host variables, which are used to hold data retrieved from or passed to the database during SQL operations. Host variables can be defined using RPG's data types and are used to bind values in SQL statements.
4. SQL Precompiler:
RPG programs with embedded SQL statements are processed by an SQL precompiler that translates the SQL statements into native database commands. The precompiler checks the syntax, validates data types, and generates the necessary code to interact with the database.
5. Commit and Rollback:
RPG supports transaction management through commit and rollback operations. A commit operation makes permanent changes to the database, while a rollback operation undoes any changes made within a transaction.

By combining file handling techniques and database access features, RPG provides a robust framework for managing data in business applications. It allows developers to seamlessly interact with files and databases, perform CRUD operations, retrieve and update data, and ensure data integrity and consistency.