I find some notes in the MVS Initialization and Tuning Reference manual as below:
IEFSSNxx contains parameters that define the primary subsystem and the various secondary subsystems that are to be initialized during system initialization.
Unless you are starting the Storage Management Subsystem (SMS), specify the primary subsystem (JES) first. Some subsystems require the services of the primary subsystem in their initialization routines.
But I find the JES2 is not start automatically in member IEFSSNxx , so the operator must start it later with a START command.
****** ***************************** Top of Data *
000100 SUBSYS SUBNAME( SMS)
000200 INITRTN(IGDSSIIN)
000300 INITPARM('ID=SP,PROMPT=DISPLAY')
000400 SUBSYS SUBNAME(JES2)
000500 PRIMARY(YES) START(NO)
000600 SUBSYS SUBNAME(LOGR)
000700 INITRTN(IXGSSINT)
000800 SUBSYS SUBNAME(RRS)
000900 SUBSYS SUBNAME(RACF)
001000 INITRTN(IRRSSI00)
001100 INITPARM('#')
in the member COMMNDxx, there is a command COM='S JES2' used to start JES2.
****** ***************************
000100 COM='DD ALLOC=ACTIVE'
000200 COM='DD ADD,SMS=(DMGROUP)'
000300 COM='S JES2'
000400 COM='S DFRMM'
000500 COM='S SDSF'
As jes2 is start according the command in the member COMMNDxx and it must be started before other subsystems.
So I am doubt which member will be read and execute first during system initialization, COMMNDxx first?
I think you are confusing "initialization" and "execution". The IEFSSNxx member is used to define (and in some cases initialize) the various subsystems, including JES. However, JES is not started until the COMMNDxx member START command is executed. If you have access to a system console, you can see during an IPL where the system generates messages about waiting for various resources which have not yet started (such as the TSO subsystem waiting for OMVS -- and possibly zFS -- to be active before allowing anyone to log on).
Thanks for your help.
Below is the IEFSSNxx member, if we change the START(NO) TO START(YES), so an automatic START command should be issued for the JES2. So can I consider the COM='S JES2' command in the member COMMNDxx is useless?
Another question, I can't find the commands like COM='S RACF' and COM='S SMS' in COMMNDxx member, so I want to know when these start commands were issued? Issued by the operator in the system console?
****** ***************************** Top of Data *
000100 SUBSYS SUBNAME( SMS)
000200 INITRTN(IGDSSIIN)
000300 INITPARM('ID=SP,PROMPT=DISPLAY')
000400 SUBSYS SUBNAME(JES2)
000500 PRIMARY(YES) START(NO)
000600 SUBSYS SUBNAME(LOGR)
000700 INITRTN(IXGSSINT)
000800 SUBSYS SUBNAME(RRS)
000900 SUBSYS SUBNAME(RACF)
001000 INITRTN(IRRSSI00)
001100 INITPARM('#')
I think you are confusing "initialization" and "execution". The IEFSSNxx member is used to define (and in some cases initialize) the various subsystems, including JES. However, JES is not started until the COMMNDxx member START command is executed. If you have access to a system console, you can see during an IPL where the system generates messages about waiting for various resources which have not yet started (such as the TSO subsystem waiting for OMVS -- and possibly zFS -- to be active before allowing anyone to log on).
