> may I know what for these DIAG calls actually,and how they are going to > help to access the dasds from other operating systems other than Linux on > Z-server.
Not quite clear what you're asking here, but here's a guess: DIAGnose calls are used to abstract some important system function into a form that can be used in a consistent way without revealing a lot of the details how the operation works, or to provide some function that may or may not be performed by hardware, but ought to look like a native part of the machine (see DIAG 8 for a good example of this use of DIAG; DIAG 8 executes a CP command and returns the output). For Linux, this mostly applies to disk I/O. The DIAG driver for Linux provides two things: a consistent abstraction for dealing with disk I/O and a shorter code path in that it relies on CP economies of scale to do a lot of work that otherwise would have to be done in Linux. The abstraction has value in that by overlaying the ability to use DIAG 250 to do disk I/O regardless of the actual disk geometry (ECKD, FBA or SCSI) and connectivity (ESCON, FICON, FCP) makes system management a lot simpler. The shorter code path comes into play in that by using DIAG I/O (which only works on VM) Linux relies on CP to optimally schedule the I/O in the most efficient way it knows how. The amount of processing that takes place in the Linux kernel is much smaller, and most of the error handling, and other code that is necessary to manage the I/O directly with other methods simply isn't necessary with DIAG I/O. CP does it for you -- you either get your block, or you don't and you get a nicely decoded error block all ready to process without a programming effort in the guest. This streamlines I/O processing, and improves throughput/performance fairly noticeably. Now, guessing about the reference to other operating systems. DIAG I/O doesn't really do anything to enable data transfer with other operating systems. The major interaction of DIAG I/O with CMS is that typically CMS tools are used to prepare disks for DIAG-style I/O (rather than dasdfmt or other items). This is very convenient for VM shops. If this isn't what you wanted to know, could you rephrase your question? ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
