Collection ID

Enhanced Definition

A Collection ID in DB2 for z/OS is a logical name that identifies a group of DB2 packages. It serves as a qualifier for packages, allowing multiple versions of the same program's package to exist within DB2, each residing in a different collection. This mechanism is crucial for managing application versions, development stages, and different environments. In DB2 for z/OS, a `Collection ID` is a logical identifier used to group one or more DB2 packages. It serves as a qualifier for packages, enabling the organization and management of executable SQL statements for application programs.

Key Characteristics

- Logical Grouping: It acts as a container or namespace for one or more DB2 packages, which are executable forms of SQL statements.
- Package Resolution: During program execution, DB2 uses the Collection ID (along with the package name) to locate the correct package to execute.
- Version Control: Allows different versions of an application's packages (e.g., development, test, production) to coexist in DB2 under distinct Collection IDs.
- Binding Process: Specified during the BIND process (e.g., BIND PACKAGE(collection_id.package_name)) to place the newly created or replaced package into a specific collection.
- Default Specification: Can be set as a default in the DB2 subsystem parameter module (DSNHDECP) or dynamically via the SET CURRENT PACKAGESET SQL statement or the QUALIFIER parameter in DSN SYSTEM commands.
- Security Context: Privileges (e.g., BINDADD, BIND) are often granted at the Collection ID level, controlling who can create or modify packages within a collection.

Use Cases

- Application Versioning: Maintaining separate collections for different releases or versions of an application (e.g., APPV10, APPV20) to facilitate upgrades and rollbacks.
- Development Environments: Grouping packages for various development, testing, QA, and production environments (e.g., DEVCOLL, TESTCOLL, PRODCOLL) to isolate changes.
- Parallel Development: Enabling multiple development teams to work on the same application simultaneously, each using their own Collection ID for their packages.
- Migration and Testing: Facilitating the migration of applications between environments by binding packages to the appropriate Collection ID for the target environment.
- Vendor Applications: Isolating packages for third-party vendor applications from in-house developed applications.

Related Concepts

The Collection ID is fundamental to DB2 Packages and the BIND process. A DB2 package is the compiled form of SQL statements, and it must reside within a Collection ID. A DB2 Plan can reference packages from one or more Collection IDs, or it can be bound using the PKLIST option, which specifies a list of Collection IDs and package names. The CURRENT PACKAGESET special register or the DSNHDECP module can define the default Collection ID for a session, influencing which packages are resolved when a program executes. It provides a layer of organization above individual packages, complementing the role of DB2 Plans in defining application execution paths.

Best Practices:

Meaningful Naming Conventions: Establish clear, consistent naming conventions for Collection IDs that reflect their purpose, application, or environment (e.g., APPLNAME_PROD, APPLNAME_TEST).
Align with Application Lifecycle: Design Collection IDs to align with your application development lifecycle, creating separate collections for development, testing, and production stages.
Control BIND Privileges: Restrict BIND privileges to specific Collection IDs to authorized personnel only, ensuring package integrity and preventing unauthorized changes.
Document Usage: Thoroughly document which applications use which Collection IDs, including their purpose and any dependencies, for easier maintenance and troubleshooting.
Optimize Package Resolution: When defining PKLIST for a DB2 plan, list the most frequently accessed Collection IDs first to potentially improve package resolution performance.