NAME    [Toc]    [Back]

       class_open - initialize the class scheduling database

SYNOPSIS    [Toc]    [Back]

       #include <apar_types.h> #include <sys/class.h>

       class_open(
               apar_t part_id,
               class_apar_handle_t *handle );

LIBRARY    [Toc]    [Back]

       Class Scheduling Library (libclass.a)

       This library is not available as a shared library.

PARAMETERS    [Toc]    [Back]

       Input  that  describes  the  unique  partition identifier.
       Output that displays the descriptor used in calls to  reference
 the partition.

DESCRIPTION    [Toc]    [Back]

       The  class_open()  function  is  used to prepare the class
       database for use as follows: Opening  the  disk  file  (if
       required)  Creating (or attaching to) a shared memory section
 Creating (or attaching to) a  semaphore  Initializing
       the database if one does not aready exist

       Before  class  scheduling can be used for a partition, its
       class database must be initialized. At the first  call  of
       class_open()  since  the system last started, the function
       creates  a  shared  memory  segment  for  the  partition's
       database  and,  if  it  exists  on disk, reads it into the
       shared memory. A semaphore is also created that is used to
       synchronize  potential simultaneous database updates (from
       class_admin and runclass, for instance).  If  no  database
       exists  for  the  partition,  one will be created with the
       default name and configuration.

       On subsequent calls to class_open(), the function attaches
       to  the  shared memory and semaphore for the database most
       recently loaded into memory for the specified partition.

                                  Note

       It is possible for multiple databases to be set up on disk
       for  use with the same partition (to be applied at different
 times). In this case, the  database  currently  loaded
       into  memory  or,  if  no  database is loaded, the default
       pathname assumed  by  the  class_open()  function  when  a
       database  is  loaded  from  disk might not be appropriate.
       Therefore, the program must call class_load_database()  to
       specify the target database.

RESTRICTIONS    [Toc]    [Back]

       The caller must have root access rights.

RETURN VALUES    [Toc]    [Back]

       The  operation  completed  successfully.  The class_open()
       succeeded but no database existed.   A  new  database  was
       created  with default configuration settings.  The calling
       process is not superuser (root) and permission is  denied.
       The  malloc  function  failed  to  get  memory for handle.
       Failed to access disk file, if it exists.  Failed to  create
  or  attach  to  shared  memory.   Failed to create or
       attach to semaphore.

SEE ALSO    [Toc]    [Back]

       Commands: runclass(1), class_admin(8)

       Functions: class_load_database(3)

       Files: class_scheduling(4)

       System Administration



                                                    class_open(3)