What are the differences between JES2 & JES3 ?

Answer Posted / echo

Some principle differences between the two JES systems
include:
In a mainframe installation that has only one processor,
JES3 provides tape setup, dependent job control, and
deadline scheduling for users of the system, while JES2 in
the same system would require its users to manage these
activities through other means. In an installation with a
multiprocessor configuration, there are noticeable
differences between the two, mainly in how JES2 exercises
independent control over its job processing functions. That
is, within the configuration, each JES2 processor controls
its own job input, job scheduling, and job output
processing.
In cases where multiple z/OS® systems are clustered (a
sysplex), it is possible to configure JES2 to share spool
and checkpoint data sets with other JES2 systems in the
same sysplex. This configuration is called Multi-Access
Spool (MAS). In contrast, JES3 exercises centralized
control over its processing functions through a single
global JES3 processor. This global processor provides all
job selection, scheduling, and device allocation functions
for all of the other JES3 systems.
With JES3, installations may decide whether the global JES3
or z/OS base control program will handle device allocation.
With JES2, only the z/OS base control program handles
device allocation.

Source:
http://publib.boulder.ibm.com/infocenter/zos/basics/index.js
p?topic=/com.ibm.zos.zconcepts/zconcepts_154.htm

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