MAINFRAME hardware architecture Evolution History {1}

This article gives a brief evolution history of zos hardware,
Main contents include: CPC, CHANNEL, STORAGE, CU, DEVICE, TAPE
You need to know how hardware is addressable;
For example, the device X address is 132.

Later, in order to increase IO performance, DIRECTOR and SWITCH were added as the intermediate buffer mechanism between channel and CU,
It should be noted that DIRECTOR, SWITHCH is a data forwarding device, high-speed

 
 

  
  
An ESCON director or FICON switch is a sophisticated device that can sustain high data rates through many connections. (A large director might have 200 connections, for example, and all of these can be passing data at the same time.) The director or switch must keep track of which CHPID (and partition) initiated which I/O operation so that data and status information is returned to the right place. Multiple I/O requests, from multiple CHPIDs attached to multiple partitions on multiple systems, can be in progress through a single control unit. 
 
 

At the same time, an io subsystem is added between the LPAR and the channel to facilitate IO management,

 
 

  
  
An I/O subsystem layer exists between the operating systems in partitions (or in the basic machine if partitions are not used) and the CHPIDs. 
 
 

IO subsystem is used to map the volume to the physical address. Zos only recognizes the device number)

 
 

  
  
The I/O control layer uses a control file known as an IOCDS (I/O Control Data Set) that translates physical I/O addresses (composed of CHPID numbers, switch port numbers, control unit addresses, and unit addresses) into device numbers that are used by the operating system software to access devices. 
 
 

About UCB:
Modern control units, especially for disks, often have multiple channel (or switch) connections and multiple connections to their devices, as shown in Figure 8. they can handle multiple data transfers at the same time on the multiple channels. each device will have a unit control block (UCB) in each z/OS image.
Note that UCB is a concept at the OS image level, which also provides a possibility for HYPAV.
For example:
The following describes the concept of drive:


Note the latest implementation of 3990CU and 3390 disks and the second figure 3390.

 
 

  
  
The 2105 unit is a very sophisticated device. It emulates a large number of control units and 3390 disk drives. It contains up to 11 TB of disk space, has up to 32 channel interfaces, 16 GB cache, and 284 MB of non-volatile memory (used for write queueing). The Host Adapters appear as control unit interfaces and can connect up to 32 channels (ESCON or FICON). 
 
 

The internal processing (to emulate 3990 control units and 3390 disks) is provided by four high-end Proteus processors in two processor complexes; each complex can operate the total system. internal batteries preserve transient data during short power failures. A separate console is used to configure and manage the unit.