BCSS
The BCSS manages I/O to the registration data sets (collectively called the REGISET), manages APF-authorized functions, and performs processing for intercepted open, close, attach, and link requests.
The BCSS performs most of the I/O to the REGISET during initialization and termination of the step execution. A small amount of I/O is performed during application program execution, mainly during checkpoint request processing. Most I/O during checkpoint processing is performed against the checkpoint data set.
The BCSS must be active on the MVS system where you want to execute application programs that use AR/CTL products and where you want to access records in the REGISET through the ISPF interface. You can use the AR/CTL Status Check utility (program AESUVBCS) to ensure that required AR/CTL products, components, and functions are available for application execution.
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