The assignment of the master attribute when a network is set up and to another specific processor when the previous master crashes can be predefined via the SET-PUBSET-ATTRIBUTES command. The specifications are stored in the SVL of the PUBRES of the SF pubsets or the VOLRES of the SM pubsets. These specifications determine how the sharer will react when the pubset is imported, when the current master processor crashes and when a pubsets is exported during a master change (EXPORT-PUBSET command with MASTER-CHANGE=*YES).
The following specifications are possible for the master attribute:
MASTER
The MASTER operand defines which processor is to be the master processor when the pubset is imported, in as far as the operand SHARER-TYPE=*STD is specified in the IMPORT-PUBSET command.
The SHOW-PUBSET-ATTRIBUTES command displays this value under
"DESIGNATED MASTER" and the current master processor under "CURRENT MASTER".BACKUP-MASTER
The BACKUP-MASTER operand can be used to define a processor which is to automatically assume the role of master after a master change.ALTERNATE-BACKUP
The ALTERNATE-BACKUP operand defines a method for selecting the backup master if at the time of the master change, no backup master can be defined or the processor designated as the backup master is not active.ALTERNATE-MASTER
The ALTERNATE-MASTER operand can be used to assign the role of the master processor to the backup master in the case that the import of the pubset is ready there before it is finished on the designated master.
Selection of actual master processor
When the IMPORT-PUBSET command is issued, the master processor is selected, after normal termination of the previous pubset session, as follows:
If a "current master" is already entered in the SVL, that specification applies.
If SHARER-TYPE=*MASTER is specified in the IMPORT-PUBSET command, the imported processor becomes the master processor.
If a "designated master" is specified in the SVL, this becomes the master processor. Exception: ALTERNATE-MASTER=*BACKUP-MASTER is specified in the SVL and the backup master is imported first – then this processor becomes the master processor.
If none of conditions 1 to 3 is met, the imported processor becomes master processor (i.e. the processor on which the IMPORT-PUBSET command is first issued becomes the master processor).
Selection of the actual backup master
At the time of a master change, the actual backup master is selected as follows:
If a "backup master" (SET-PUBSET-ATTRIBUTES command, BACKUP-MASTER operand) is entered in the SVL and if that processor is an active slave processor, it becomes the backup master.
If the "backup master" entered in the SVL is the current master, the MASTER (= designated master) entered in the SVL is the backup master
If no "backup master" is entered in the SVL or if that processor is not active, the SVL ALTERNATE-BACKUP entry is evaluated:
ALTERNATE-BACKUP=*NONE
There is no alternative backup master, no master change takes place.ALTERNATE-BACKUP=*BY-SHARER
The processor that is the first active sharer in the current SVL sharer list becomes backup master.ALTERNATE-BACKUP=*BY-OPERATOR
No backup master is defined; a master change is not initiated automatically but must be started by systems support by means of an import with master change (see "Setting up a shared pubset network").
After a successful master change, the backup master is the new master processor (i.e. current master), otherwise it remains a slave processor.
The master change is rejected there is no CCS connection between the backup master and a slave processor (it has not been established or it has been interrupted).
If an automatic master change is not initiated or fails, the pubset is put into INACC,QUIET status.
If a master change is not explicitly prohibited (by the specification BACKUP-MASTER=*NONE and ALTERNATE-BACKUP=*NONE), or if a master change is not initiated or fails, it can be initiated subsequently by the commands EXPORT-PUBSET or IMPORT-PUBSET with MASTER-CHANGE=*YES (see chapter “Administration of MSCF networks”).