shared memory synchronisation

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class_open

class_open(3)						     Library Functions Manual						     class_open(3)

NAME

       class_open - Initialize the class scheduler database.

SYNOPSIS

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

       class_open(
	       apart_id,
	       part_id,
	       *class_apar_handle_t,
	       handle );

PARAMETERS

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

DESCRIPTION

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

       Before class scheduling can be used for a partition, its class scheduler 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 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 configuration

       On subsequent calls to class_open() the function attaches to the existing shared memory and semaphore.

RESTRICTIONS

       The caller must have root access rights.

RETURN VALUES

       Operation successfully completed.  The class_open succeeded but no database existed.  A new database was created with default configuration
       settings.  The calling process is not super user (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

       class_scheduling(4), runclass(1), class_admin(8) delim off

																     class_open(3)

UNIX for Advanced & Expert Users