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)