IMS environments and configurations

IMS contains two major components that can be used together or separately: the IMS Database Manager (DB) and the IMS Transaction Manager (TM). When you use them together, they constitute the DB⁄DC environment.

Using the Database Manager alone, you can generate the batch environment and the database control (DBCTL) environment. Using the Transaction Manager alone, you can generate the data communication control (DCCTL) environment. Data sharing and the Extended Recovery Facility (XRF) are often considered environments, but they are special cases of the three environments listed here.

In addition to the three environments (DBCTL, DB/DC, and DCCTL), you can configure IMS as an IMSplex.

Use the major components of IMS to configure your environment as part of your system definition process, based on your business needs.

The DB/DC, DCCTL, and DBCTL environments are all considered online IMS systems.

Each of the IMS environments is a distinct combination of hardware and programs that supports distinct processing goals. The online environments and the goals they support are shown in the following table.

Table 1. IMS online environments
Environments	Data processing goals
DBCTL (See DBCTL environment)	Process network transactions without the Transaction Manager—that is, use the Database Manager with a transaction management subsystem (for example, CICS®). Run batch application programs using DB batch at certain intervals (for example, process a payroll or produce an inventory report). Run database utilities using DB batch.
DB⁄DC (See DB/DC environment)	Enable terminal users to retrieve data and modify the database with satisfactory real-time performance. (Some typical applications are banking, airline reservations, and sales orders.) Ensure that retrieved data is current. Distribute transaction processing among multiple CPUs in a communications network. Run batch application programs using DB batch at certain intervals (for example, process a payroll or produce an inventory report). Run database utilities using DB batch. Run application programs that access external subsystems or access data in external subsystems, such as data in Db2 for z/OS®.
DCCTL (See DCCTL environment)	Process network transactions without the Database Manager by using the Transaction Manager with an external database management subsystem. Maintain system log information for restart by using DBRC. Run application programs that access external subsystems or access data in external subsystems, such as data in Db2 for z/OS.