RELEASE.NOTES

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                     **  PROGRAMMING NOTE  **


  Don't forget to update "hercnot.html" with the below information too!


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                     Version 4.0 RELEASE NOTES


* The new minimum supported Microsoft Windows platform is now Windows XP or
  greater. Windows 98, Windows NT and Windows 2000 are no longer supported.


* The combination of NUMCPU and MAXCPU controls the behavior of how many
  CPU engines will be configured online upon startup and how many can be
  configured online later. In previous versions this was controlled via
  the NUMCPU statement and the compile-time constant 'MAX_CPU_ENGINES'.

  For compatibility with previous versions if MAXCPU is not specified its
  value defaults to NUMCPU. If neither is specified it defaults to 1.


* Most configuration file statements are now available as and processed as
  panel commands. Most valid configuration file statement may now also be
  entered as a panel command. Most panel commands however are allowed
  as configuration file statements. See the documentation for details.


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                     Version 3.06 RELEASE NOTES


* Tape "AUTOMOUNT" support

  Starting with Hercules version 3.06 a new AUTOMOUNT option is available
  that allows guest operating systems to directly mount, unmount and query
  tape device filenames for themselves, without any intervention on the
  part of the Hercules operator.

  Automount support is enabled via the AUTOMOUNT configuration file statement.

  An example guest automount program for VSE called "TMOUNT" is provided in
  the util subdirectory of the Hercules source code distribution.

  Briefly, the 0x4B (Set Diagnose) CCW is used to mount (or unmount) a file
  onto a tape drive, and the 0xE4 (Sense Id) CCW opcode is used to query the
  name of the currently mounted file.

  For mounts, the 0x4B CCW specifies the filename of the file to be mounted
  onto the drive. The file MUST reside in the specified AUTOMOUNT directory
  or the automount request will be rejected. To unmount the currently mounted
  file, simply do a mount of the special filename "OFFLINE".

  To query the name of the currently mounted file, the 0xE4 CCW is used. Note
  however that the 0xE4 (Sense Id) CCW opcode cannot be used by itself since
  the drive may also already natively support the Sense Id CCW opcode. Instead,
  it must be preceded by (command-chained from) a 0x4B CCW with a data transfer
  length of one byte. The following 0xE4 command is the one that then specifies
  the i/o buffer and buffer length of where the query function is to place the
  device's currently mounted host filename.

  In summary:


      MOUNT:      X'4B', <filename>, X'20', <length>

      UNMOUNT:    (same thing but use filename "OFFLINE" instead)

      QUERY:      X'4B', <buffer>, X'60', 1
                  X'E4', <buffer>, X'20', <buffersize>


  Again please refer to the provided TMOUNT program for a simple example
  of how automount support might be implmented on a guest operating system.

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                     Version 3.05 RELEASE NOTES


* The 'conspawn' utility used to process 'sh' commands now recognizes a
  specially designed keyword "startgui" to accomodate automatic starting
  of Windows GUI applications via the .RC file or panel command-line.

  If the first word following 'sh' is "startgui", then the "ShellExecute"
  API is used to start the requested program rather than the 'system()'
  API as otherwise.

  The "startgui" keyword must always be used to start any Windows program
  that is not a command-line program. Hercules, itself being a command-line
  program, monitors the 'stderr' and 'stdout' pipes so it can log messages
  received from either pipe directly to the Hercules console log. Programs
  such as notepad however, because they are not command-line programs, do
  not use stdout/stderr thus causing Hercules to hang if "start" is used
  instead.

  This rule applies regardless of how Hercules itself is started (i.e. via
  HercGUI or directly via the command-line) and regardless of whether the
  "start" command is wrapped in a batch file or not. That is to say, using
  the Hercules command "sh batchfile foobar" to start your batch file which
  then does "start notepad %1" still causes Hercules to hang until notepad
  first exits. Instead, you should ask Hercules to "sh startgui batchfile",
  and let the batchfile start notepad however it wants.


* Real SCSI tape drives used with Hercules must provide a certain minimum set
  is "IBM compatible" support in their SCSI command set/behavior in order to
  work properly with Hercules. Furthermore, the Hercules device-type used on
  your device statement in your Hercules configuration file should match the
  the level of support/behavior that they provide.

  For example, all SCSI tape drives used with Hercules must provide the ability
  to set variable-length blocks as well as long erase-gaps (long erase-gaps
  allows new data to be appended to the end of existing data without having to
  write a tape-mark to separate the new data from the old existing data first).

  Another example would be using a model of SCSI tape drive that happens to
  report physical block-id values in a format different from the way real IBM
  mainframe tape drives report them. 3480/3490 tape drives for example report
  their block-ids (used in Read Block Id and Locate CCWs) in a very specific
  format wherein bits 1-7 of the high-order byte of the reported 4-byte block-
  id indicates the tape's physical "segment" location of where the lower 22-
  bit block number is physically located on the tape. (The block-id segment
  is used to allow the tape drive to quickly position itself to the approximate
  location where the desired block acually resides on the tape and thus allows
  high-speed positioning for the Locate CCW).

  If the model of SCSI tape drive you are actually using with Hercules does not
  use this same block-id format however, then it cannot be used with Hercules
  as a 3480 or 3490 model tape drive with specially defined options.

  If the SCSI tape drive you are using reports its block-ids using a 32-bit
  block-id value (the same way a 3590 model tape drive does), then similarly,
  it should be defined to Hercules as a model 3590 device-type as well (since
  that is how it is behaving with respect the format of the returned blockid
  values). It you wish to define it in Hercules as a model 3480 or 3490, then
  you will need to use specially defined options before it will work properly
  as the model drive you wish it to emulate.

  With all that being said, it should be noted that PARTIAL support for 3590
  device emulation is possible with judicious use the aforementioned special
  options, but full/complete 3590 support is unlikely due to lack of publicly
  available documentation. Details regarding 3590 CCW handling is restricted 
  (confidential) IBM proprietary information, and is not normally available
  outside of IBM. Not long ago IBM was required by US law to publish such
  information, but unfortunately for Hercules, such is no longer the case.

  For further information regarding use of SCSI attached tape drives with
  Hercules and their associated specially defined options, please refer to
  the section on SCSI tape drives in the Hercules's Device Configuration
  documentation.


* In order to ensure proper functioning of the TOD clock with older versions
  of guest operating systems, the default values of Hercules's internal thread
  priorities for the Windows version of Hercules were changed to be identical
  to those used by all other supported platforms. Originally, the default
  thread priority values for the Windows version of Hercules were:

            ***  3.04 (and prior) Default Priorities  ***

            Thread    Priority           Meaning
            -------   --------   ------------------------
            HERCPRIO     0        Normal Process priority

            DEVPRIO     -8        Above Normal  Thread priority
            TODPRIO      0        Normal        Thread priority
            CPUPRIO      0        Normal        Thread priority

  which caused acceptable performance/functioning on most, but not all, guest
  operating systems. Beginning with version 3.05 however, the prioriries now
  default to:

            ***  3.05 (and later) Default  Priorities  ***

            Thread    Priority           Meaning
            -------   --------   ------------------------
            HERCPRIO     0        Normal Process priority

            TODPRIO    -20        Time Critical  Thread priority
            DEVPRIO      8        Below Normal   Thread priority
            CPUPRIO     15        Lowest         Thread priority

  which may on more modern guest operating systems (which handle the TOD clock
  differently than do older less sophticated versions) cause a slight decrease
  in overall performance. If such is the case, the original default priorities
  (and thus the original behavior) can be obtained via addition of appropriate
  HERCPRIO, TODPRIO, DEVPRIO and CPUPRIO control file statements with values
  identical to the original version 3.04 default values.


* Additional configuration file usability enhancements have been implemented
  in the form of a new 'INCLUDE' (and associated 'IGNORE') statement, allowing
  configuration files to "include" statements from a different named file.

  Additonally, a new "enhanced" symbolic substitution syntax is now also
  supported. Refer to the Hercules "Configuration File" documentation for
  further information and details.

  A rather nifty "Automatic Operator" facility has also been implemented in
  the current release as well. While not exactly a "configuration file
  usability enhancement", it is nevertheless something we hope might prove
  to be more useful/helpful to our many users. See the "README.HAO" document
  for more information.

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                     Version 3.01 RELEASE NOTES


- Support for z990 crypto instructions is conditional on the presence of the
  glibcrypt library.

  If Hercules is BUILT, the development files for glibcrypt should be available.

  When hercules is RUN, the runtime files for glibcrypt should be installed.

  Depending on the level of glibcrypt used to *build* hercules, the associated
  level of glibcrypt should also be present on the target machine. On systems
  supporting shared library versioning, multiple levels of the glibcrypt
  runtime libraries can be installed simultaneously, ensuring availability
  of the z990 crypto instructions, regardless of the level of glibcrypt with
  which hercules was initially built.


- CTC and LCS devices now ++MUST++ specify ALL addresses on the configuration
  statement.

  Example:

    0A00.2     LCS .....
    0B00.2     CTCI ....

     or

    0A00.4     LCS -oat hercules.oat

     or

    0A00-0A03  LCS -oat hercules.oat

     or

    0A00    LCS -oat hercules.oat
    0A01    LCS
    0A02    LCS
    0A03    LCS

  Previously (i.e. with version 3.00), only the first (even numbered) device
  needed to be defined and Herc would automatically define the odd numbered
  device for you. Starting with Hercules version 3.01 however, you now need
  to define BOTH devices, just like you did with versions prior to 3.00.

  Once again, starting with version 3.01, you **MUST** define BOTH DEVICES.

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                     Version 3.00 RELEASE NOTES


- Reminder that CTCI device handling was changed as follows:

  - The CTCI-W32 protocol is deprecated. You should use the CTCI protocol
    instead.

  - You MUST NOT define both even/odd CTCI device pairs in your configuration
    file. You should ONLY define the first even numbered device. Hercules will
    automatically define the odd numbered device for you. If you define the
    odd numbered device by mistake, an open error will occur on that device.
    This is by design. See the README.NETWORKING document for further details.


- Hercules Dynamic Loader support: starting with version 3.00, Hercules now
  contains support for the dynamic loading of certain modules upon startup on
  some platforms (e.g. Linux and Windows for example). As a result of this new
  feature, "Hercules" itself now no longer consists of just the 'hercules.exe'
  module by itself, but rather consists of BOTH the 'hercules.exe' program AS
  WELL AS whatever dynamic modules (DLLs) that accompany it.

  As a result if this change, whenever you install a new version of Hercules,
  you must ensure that you ALSO install the accompanying new versions of the
  new dynamic modules as well. Attempting to use a version of Hercules with a
  dynamic module that was not specifically built for that version will cause
  loading of that dynamic module to fail.

  You CANNOT mix versions of Hercules with differing versions of dynamically
  loaded modules.

  Ensure that your library path LD_LIBRARY_PATH is set correctly such that it
  includes the directory of your Hercules executables. Especially, message
  HHCCF042E will indicate that system is unable to locate necessary loadable
  modules.


- ECPS:VM: Do not use ECPS:VM (See README.ECPSVM) in an AP or MP environment
  in VM/370. If AP=YES or MP=YES is coded in DMKSYS and the AP/MP control
  file is used to build the CP nucleus and NUMCPU is set to more than 1 in
  the hercules.cnf file, any of LOK001, LOK003 or other abends will occur.
  This occurs because the Hercules ECPS:VM CP Assist implementation is not
  MP safe, and particularily, attemps VM dispatching without holding necessary
  AP or MP locks.


- Due to the change in Hercules' "mainstor" memory allocation technique to
  address a "double memory consumption" bug in Cygwin's malloc implementation,
  some Windows Hercules users may experience an "out of memory" error whenever
  Hercules is started with a large MAINSIZE configuration file value:

      "HHCCF031S Cannot obtain nnnMB main storage"

  This error will most likely occur (if it does at all) for those users who
  have manually adjusted their Cygwin "heap_chunk_in_mb" Windows registry
  setting value (in order to allow them to specify a large MAINSIZE value
  when running Hercules). If this problem does occur (i.e. if you DO happen
  to experience the above mentioned "HHCCF031S Cannot obtain main storage"
  error with this new release of Hercules), then either REDUCE your "heap_
  chunk_in_mb" value (yes, that's correct: REDUCE it; i.e. change it to a
  SMALLER value) or else remove it altogether (so as to let it default).

  Detailed explanation:

  History/background: Cygwin has a built-in limit to the amount of memory
  that may be allocated in one chunk. If you try 'malloc'ing more than this
  limit, you will receive an "out of memory" error. Since many Hercules users
  specify large MAINSIZE values in their configuration file, they sometimes
  experience this problem.

  The suggested workaround to this "problem" was to add a "heap_chunk_in_mb"
  registry value to Cygwin's registry settings with a large enough value such
  that Cygwin would then be able to satisfy Hercules' 'malloc' request for
  such a large MAINSIZE value.

  This worked fine until sometime around version 1.3.15 of Cygwin, at which
  time they began using a different 'malloc' technique that unfortunately
  causes TWICE as much Windows virtual memory to be allocated for any large
  memory allocation (the technical reasons of which are explained in comments
  in source member config.c where mainsize is being allocated).

  In order to address this double memory allocation issue in Cygwin's malloc
  implementation, Hercules was changed to use mmap to allocate its mainstor
  rather than malloc (which, unlike malloc, does NOT inadvertently allocate
  twice as Windows virtual storage than was requested), which did indeed re-
  solve the "double memory allocation" problem.

  Unfortunately however, because Cygwin's malloc and mmap logic each consume
  completely different portions of Windows' virtual memory, the more memory
  that is reserved for malloc usage (via using a larger "heap_chunk_in_mb"
  value), the LESS becomes available for mmap usage!

  Thus, while increasing your "heap_chunk_in_mb" registry value USED to HELP
  [to allow you to allocate larger amounts of mainstor (MAINSIZE)], it NOW
  causes the complete OPPOSITE effect: it ends up PREVENTING you from being
  able to 'mmap' as much storage as you'd like to have!

  Conclusion:

  Therefore, if you are currently using the "heap_chunk_in_mb" registry value
  setting to allow you to allocate large MAINSIZE values, then starting with
  version 3.00 of Hercules you need to DESCREASE your "heap_chunk_in_mb" value
  (or remove it altogether and let it default) in order to leave enough memory
  remaining for Hercules (Cygwin actually) to be able to satisfy its 'mmap'
  request for your desired MAINSIZE amount.
  
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