EFS Systems on a Linux Base: Getting Started

Chapter 1. Introduction 7

1.5 EFS limitations

There are a number of functions not available for EFS systems. These include:

򐂰 Parallel Sysplex®, Coupling Facility processors, and Coupling Facility links are not

available.

򐂰 FICON™ channels are not available.

򐂰 Unique control unit hardware functions are generally not emulated, such as the cache and

compression functions of 3990-6 control units.

򐂰 Advanced zSeries (and S/390) hardware recovery functions, such as multiple I-units in

processors and the Application Preservation Feature, are not emulated.

򐂰 Cryptographic hardware adapters or coprocessors are not available.

򐂰 OSA-Express functions are not available.

6

򐂰 HiperSockets™ are not available.

򐂰 LPARs are not available. However, if sufficient memory is available in the PC, we can

simultaneously emulate multiple z/Series machines. This is not quite the same as using

LPARs in a zSeries system, but it is similar in many ways. The multiple emulated systems

can communicate with each other over the LAN or by emulated CTC connections.

򐂰 The new and altered instructions in the zSeries z990 systems are not available at the time

of writing.

򐂰 Multiple paths to a device are not supported.

FLEX-ES has formal support only on specific xSeries models and specific ThinkPad models.

FSI adds to the list of supported models over time. This is discussed in more detail in the next

chapter.

1.6 Detailed FLEX-ES overview

This section provides a slightly more detailed description of FLEX-ES than was presented

earlier. FLEX-ES can be viewed as the following components:

򐂰 A S/390 instruction emulator, which is the heart of the system. It examines each S/390

operation code and emulates that operation, using the instructions of the underlying PC

processor.

򐂰 A resource manager that controls the interfaces between the emulated S/390 processors

and emulated I/O devices and connections.

򐂰 Emulators for various S/390 I/O devices.

򐂰 A FLEX-ES console for controlling FLEX-ES startup and operation. (This is not related to

the z/OS master console.)

򐂰 A Terminal Solicitor program that emulates local, channel-attached, non-SNA 3270

terminals. The actual terminals are TN3270e sessions that connect to this program

through normal TCP/IP protocols.

򐂰 A number of utility programs to help set up and run the FLEX-ES environment.

Figure 1-3 provides a simplified view of FLEX-ES operation. FLEX-ES is simply a process

7

under Linux. While this illustration should not be taken too literally, it can be used to make a

number of basic points about FLEX-ES.

6

Basic OSA functions over Ethernet and token ring are available.

7

It is actually a number of interrelated processes and threads, but this detail can be ignored at the conceptual level.

8 EFS Systems on a Linux Base: Getting Started

Figure 1-3 Conceptual view of FLEX-ES system

Key points include:

򐂰 FLEX-ES is a software product.

8

All the hardware shown (in Figure 1-3) is standard PC

hardware. (The hardware dongle required by FLEX-ES is not shown in the figure.)

򐂰 The FLEX-ES program emulates a complete S/390 environment.

– FLEX-ES obtains sufficient Linux virtual memory to emulate the “real memory” for the

defined S/390 machine being emulated. While not detailed in the illustration, FLEX-ES

can also emulate S/390 expanded memory.

– FLEX-ES, as part of emulating a S/390, handles S/390 I/O instructions and emulates

the S/390 I/O devices as required. In the illustration, various 3390 volumes (containing

z/OS and so forth) are contained on the PC’s disks.

򐂰 The FLEX-ES license specifies how many PC processors may be used (at any one

instant) for S/390 emulation. For a ThinkPad EFS system, this is one processor. For an

xSeries EFS system, this can be multiple processors.

򐂰 The owner can elect to

dedicate server processor(s) to FLEX-ES S/390 use. This

provides a performance boost. You cannot dedicate all the PC processors to S/390,

because other Linux functions need access to a processor. If processors are not

dedicated, then the normal Linux dispatching function dictates which processors are being

used by FLEX-ES at any instant. This number never exceeds the number permitted in the

FLEX-ES license. A ThinkPad EFS system has only a single processor, and it cannot be

dedicated for S/390 emulation.

򐂰 You can emulate a S/390 with a number of CPUs. This number cannot exceed the number

of server processors licensed for S/390 emulation. With the ThinkPad EFS system we are

8

The optional S/390 channel adapters available for use with FLEX-ES are ignored in this discussion.

PC Processor(s) in Server

Enet Adapt

Linux operating system

FLEX-ES processes

Emulated S/390

running z/OS

and its associated

applications

other Linux

processes

FLEX-ES

Terminal Solicitor

TCP/IP

LAN

Display and

keyboard

PC disks

PC Memory