On Thu, 9 Feb 2012 12:06:03 -0600, Paul Gilmartin <[email protected]> wrote:
>I had thought everything in the VM spool had carriage control (actually a CCW >opcode). But I defer to your experience. Perhaps IPL is unaffected by the >CCS opcode present in the spool. All user data in the VM spool has carriage control because the only way to get data from a virtual machine to the spool is via a virtual PUNCH or PRINTER. (System data files are excluded from this discussion.) And, yes, the spool contains the CCW opcode and data that the guest (or in some cases, CP) put there. CMS functions such as PRINT and PUNCH generate the CCWs and do the I/O to place the user data in the spool. The only thing that limits the CCWs is the virtual device type. The spool is just a holding area. Generally speaking, punches and printers put data in. A virtual reader takes data out. Virtual punches are limited to 80 characters since VM simulates a 2540. Virtual printers can have a variety of lengths, depending on device type (1403, 3211, 3800, etc.). Virtual AFP printers will accept 32K records if the cc character (machine code) is 0x5A. This is what PSF uses to write LIST38xx files. Because the virtual reader is a 2540, it cannot read records more than 80 bytes. Accessing spool files that contain those 0x5As must be done using the DIAGNOSE 0x14 interface to the spool. IPL from the virtual reader works like IPL from disk, except that CP has to figure out what part of the spool file is "data". As long as the CCW in the spool is a "data mover" (e.g. WRITE), that data will be read in by IPL. If there are any no-ops, they are skipped since they (in the real world) don't exist. >Everything in CMS has records, but some processing, e.g. FTP BINARY STREAM, >will ignore record boundaries. Everything in the minidisk filesystem (EDF) and in the Shard File System (SFS) has records. The POSIX-conformant Byte File System (BFS) does not. BFS is where you store data when the VM system is simply being used as a data repository. Alan Altmark IBM ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
