Z/Os architecture includes all of ESA/390 and the following extensions
• IBM’s high-end server OS
• Robust IBM e-server Z series mainframe OS for e-business
• Highly secure scalable high performance base to deploy internet + java technology-enabled applications
• Z/OS takes advantage of latest open s/w technologies like EJB/XML/HTML/UNICODE/IP network etc.
• Cryptographic services and distributed print services, storage management, and parallel sysplex availability
• 64 bit general registers and control registers
• 64 bit addressing mode in addition to 24 bit and 31 bit addressing modes of ESA/390 which are carried forward to Z/OS architecture
• The program status word (PSW) is expanded to 16 bytes to contain larger instruction address
• Upto three levels of DAT tables called Region Tables for translating 64 bit virtual address
• Trimodal addressing as against bimodal addressing
• Ability to switch between 24, 31, and 31 bit addressing
Logically a system consists of the main storage, one or more CPUs and channel subsystems.
Addressing: Absolute, real and virtual
Address translation converts virtual addressing to real addressing and prefixes converts real addressing to absolute addressing
A 24 bit or 31 bit virtual address is expanded to 64 bits by appending 40 or 33 zeroes on the left before it is translated by means of DAT process and 24 and 31 bit absolute address is expanded to 64 bits before its is transformed by prefixing. A 24 or 31 bit absolute address is expanded to 64 bits before main storage is accessed
2 comments for “Z/Os an introduction”
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@chels I know what you mean, its hard to find good help these days. People now days just don’t have the work ethic they used to have. I mean consider whoever wrote this post, they must have been working hard to write that good and it took a good bit of their time I am sure. I work with people who couldn’t write like this if they tried, and getting them to try is hard enough as it is.
August 24th, 2010 at 4:59 am