4.7. Media Manager, Open, Close, EOV in VSAM
Media Manager is the I/O driver code. It stands between the access method and the Input Output Supervisor. VSAM has two I/O drivers depending on the required function:
Block Processor (SVC 121), that is old and there is a SOD for being inactivated. Since z/OS V1R4 DFSMS Block Processor is being used only for Improved Control Interval processing (ICI).
Media Manager, which is modern. There is a trend to all access methods to use Media Manager. Media Manager has the I/O channel program support for implementing Extended Format.
Media Manager executes all these functions:
Creates Channel Programs with virtual addresses (this was done before by VSAM)
Page-Fix (or Page-Free) buffers
Verifies that buffers are ...
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