DL/I (Data Language/I) plays a pivotal role in IMS DB (Information Management System Database) as it serves as the primary interface for accessing and manipulating database data. DL/I provides a comprehensive set of commands and functions that enable application programs to interact with IMS DB efficiently. Here are the key roles and functionalities of DL/I:

Data Access : DL/I allows application programs to access database data by providing commands for reading, writing, updating, and deleting database records. These commands enable programs to perform a wide range of database operations, such as retrieving customer information, updating inventory records, or processing transactions.

Hierarchical Data Navigation : IMS DB utilizes a hierarchical database model where data is organized into parent-child relationships. DL/I provides commands for navigating through the hierarchical structure of the database, allowing programs to traverse parent-child relationships and access data at different levels of the hierarchy.

Data Retrieval : DL/I enables efficient data retrieval by providing commands for specifying search criteria and accessing data based on various criteria, such as key values or segment occurrence numbers. These commands allow programs to retrieve specific data records or subsets of data from the database quickly and accurately.
Data Manipulation : DL/I supports data manipulation operations by providing commands for inserting, updating, and deleting database records. These commands allow programs to modify data within the database, ensuring that the database remains up-to-date and reflects changes made by application programs.

Concurrency Control : DL/I includes mechanisms for managing concurrent access to database data to prevent data corruption and ensure data consistency. DL/I provides commands for acquiring and releasing database locks, allowing programs to control access to shared data resources and coordinate access between multiple programs.

Error Handling : DL/I includes error handling mechanisms that allow programs to detect and respond to errors that occur during database operations. DL/I provides error codes and status indicators that indicate the outcome of database operations, enabling programs to handle errors gracefully and take appropriate action as needed.

Batch Processing Support : DL/I supports batch processing by providing commands and facilities for processing large volumes of data in batch mode. Batch programs can use DL/I commands to access and manipulate database data efficiently, enabling organizations to perform batch processing tasks such as data extraction, transformation, and loading.