Memory Area Status Table (MAST)

The memory area status table (MAST) is located in memory with a write hardware register instruction. Each entry in the MAST contains information that is related to a memory area that is known to the system.

The operating software (MCP) must assign a memory area status table entry to each physically contiguous region of memory allocated and described by an Original-type Memory Area Table Entry. Portions of the defined MAST entry are managed by and used only by the operating software, while other fields are used by the hardware. The count of I/O operations in process field, for example, is managed by the CIO and IOC instructions and is typically used by the operating system to determine if the memory region may be relocated in physical memory or rolled out to secondary storage.

V3x0, V4x0, V5x0 Memory Area Status Table Layout

Digit Bit Purpose
00-01 Hardware Lock for use by processor
02 3 Memory Area Present
2 To Be Rolled Out
1 Reserved
0 I/O Inhibited memory area
03-05 Software Usage
06-09 Number of I/O's in process to this memory area
10-13 Task Number of owner
14-19 Environment Number of original
20-21 Memory Area of original
22-25 Memory Area Size
26-39 Available
processor_state/mast.txt · Last modified: 2011/08/18 17:14 by scott
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