In z/OS there are three “types” of storage, depending on the address of the storage -
- Storage with addresses from 0 to FFFFFF
- Storage with addresses from 1000000 to 7FFFFFFF
- Storage with addresses greater than 100000000
The address 1000000 is referred to as the “line,” the address 80000000 is referred to as the “bar.”
The term AMODE specifies the “addressing mode” for the module; the number of bits the module can use to address storage. The term “RMODE” refers to the “residency mode,” the location in storage where the module can be loaded.
AMODE 24 means the module uses 24 bits to address storage below the line. These programs were written to run in System/360. AMODE 31 means the module uses 31 bits to address storage below the “bar.” Rarely seen are AMODE 64 programs.
RMODE 24 programs must be loaded in storage below the line. These programs were written for OS/360, or they contain data areas, such as a DCB, that must be below the line to be used.
RMODE ANY programs can be loaded into any storage address below the “bar.” They are usually loaded above the “line,” but they can be loaded below the “line” if no above the line storage is available.