Kernel 2.2 based

• It is strongy recommended not to share tape devices. No assign/unassign functionality is implemented in the tape driver. Therefore if a tape device is shared between different instances of operating systems there is no protection against parallel access.

• When there is IO on the CTC connection and the REMOTE side does not correctly shut down (i.e. IPL without ifconfig ctcx down or there is a system crash) the local CTC device driver may enter into a hung condition. To recover from this situation, the local side must also shut the connection down (ifconfig ctcx down).
• The current implementation of the CTC network device driver can handle up to 8 CTC connections and/or 8 ESCON connections. In autosense mode the driver always picks 16 Parallel / ESCON channels with the lowest Subchannel IDs. When a CTC definition is in the kernel parameter file, the channels have to be in the first 256 CTC / ESCON Sub/channel ID's. This value (MAX_CHANNEL_DEVICES) can be changed in the ctc.c file.
• When the CTC driver is statically linked into the kernel CTC options cannot be specified in the Kernel parameter file which is used as input for SILO on native systems. Otherwise LINUX for S/390 cannot be booted. A solution for this problem is to use the CTC module instead of linking the CTC driver statically into the kernel.
• Setting up a CTC or ESCON connection (with ifconfig up) may require several retries (calling ifconfig down on both sides first).

• You may run into problems if you use DASDs with faulty tracks or records, particularly old 3380 and 3390 devices. Furthermore, alternate tracks are not supported.
• OS/390 will also flag the device as RESERVE during a backup.
• If the system has problems recognizing a newly formatted DASD re-IPL without subsequent formatting.
• Formatting

  It is recommended to format only one DASD at a time.

• At most 2GB of a swap device will be used for swapping.
• The size of any swap file may not exceed 2GB.

• The limit for the main storage that can be defined is slightly less than 2GB. (The actual limit seems to be 1919MB) For G5 and G6 this can be fixed by an micro code upgrade.

• The flag '-fno-caller-saves' must be set.
• Many programs are not ANSI C++ conform. gcc-2.95.2 is stricter about this than previous compilers widely used on Intel systems (egcs). To compile such programs use -fpermissive and check on Intel with gcc-2.95.2, before considering it to be a s390 specific bug.

• The Hardware Console is intended to be used only to bring up the system. After IPL and configuring your network connection, you should use a Telnet session to operate the system and pass commands to it.
  Applications such as vi are not supported because of the HWC's line mode nature.
• Displaying large files might cause some missing sections within the output because of the latency of the hardware interface employed by the device.
• In native or LPAR environments, you occasionally have to use the Delete button of the GUI on the Service Element or Hardware Management Console to enable further output. This is relevant to:
  • SE version 1.6.1 or older on G5, G6, and Multiprise 3000.
  • SE version 1.5.2 or older on G3, G4, and Multiprise 2000.
• Messages concerning the Hardware console operation that are generated by the Hardware console driver, cannot be provided to the syslog and are therefore unavailable with dmesg.
• Output from the head/top is deleted if the amount exceeds approximately 30 Kbyte per LPAR (or image) on SE or HMC.

• This driver only works in combination with VM. In a single image or in LPAR mode the 3215 terminal device driver initialization function just exists without registering the driver.
• The 3215 terminal device driver always uses the EBCDIC code page 037 (U.S. International) to communicate with the device. Make sure that your terminal emulation software is correctly set up to use this code page.
• X3270
  If you are accessing the console using x3270, then you should add the following settings to the .XDefaults file in order to get the correct code translation:

  ! X3270 keymap and charset settings for LINUX
  x3270.charset: us-intl
  x3270.keymap: circumfix
  x3270.keymap.circumfix: :<Key>asciicircum: Key("^")\n
  

• While VM allows you to define up to 64 virtual S/390 processors per guest machine, LINUX for S/390 currently provides support for a maximum of 32 processors only.

• To avoid filling up you disk space and to improve the system performance in out of memory situations you should consider to set the corefile size to 0. The command you need to do that is dependent of the shell you are using. For the bash is the command "ulimit -c 0" in the file /etc/profile.

• To use this driver, a running TCP/IP service machine is required on the one side, and on the other side, LINUX for S/390 must be running under VM.
• IUCV is limited to 20 connections.

• LINUX for S/390 cannot run with a root file system mounted via NFS when the network connectivity is established via LCS, because the LCS driver is delivered as an object-code-only module.
• To use OSA-2 Devices when running LINUX for S/390 on a basic mode machine (no LPARs) you need to specify an ipldelay=xxm boot parameter. We recommend a value between 2 and 5 for xx for the OSA-2 card to settle down after LOAD.

• If expanded storage is not available, XPRAM cannot be used. Its initialization fails with a log message reporting the lack of expanded storage.

• Currently, there is only support for up to 16 Token Ring or Ethernet devices.
• With some OSA H/W it is impossible for two or more guests to communicate with each other via the OSA card they have shared between them. This is because there is no hardware shortcut such that the card can microcode can sniff outgoing packets from one guest & pass them over to the other guest.

  Circumvention
  The workaround for this is to make an ip route to the other machine "route add <other_machines_addr> gw <gateway_addr>" and do the same on the other machine. Alternatively in cases tested it was found that configuring the OSA card as half duplex allowed the guests to communicate with each other.

• Recommendation: We strongly recommend not to share devices with production system. See here for more details.

• The IEEE emulation (running on machines without IEEE floating point hardware (i.e. pre-G5 machines)) does not support handling of denormalized IEEE floating point numbers. Furthermore the IEEE emulation does not provide floating point exception handling.

• When IPLing from the virtual reader of VM/ESA, with a parameter file that spans more than one line, make sure that a blank character precedes any kernel parameter. To avoid errors you should start on column 2 of the parameter line.
• When IPLing from disk or tape using an ASCII encoded parameter file which you have generated on a UNIX or PC operating system, make sure, that your line contains no special characters like tabs or newlines. In particular your parmfile cannot span over more than one line and must not be larger than 1023 Bytes.

• Multicasting has to be switched on in the kernel.
• The Gigabit Ethernet Driver needs QDIO base support.
• Starting with microcode level 0146, OSA-Express QDIO require a portname to be set in the device driver. This portname is specified using "portname:FOOBAR" in the qeth_options module parameter (see Device Drivers and Installation Commands).
• HiperSockets support is not available for kernel 2.2, but for kernel 2.4 only.
• Broadcast functionality is only available on OSA-2 hardware, not on OSA-Express QDIO.
• For further information see documentation.