SAP OSS Note 39412 version 0026 contains details of a know issue related to How many work processes should be configured?
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This note answers the following questions:
,,How many work processes must and may be configured?
,,How do I see which work processes exist and what they do?
,,How do I set the number of work processes?
Cause of the problem and Pre-requisites
Definition: In this note, "server" is a synonym for "instance".
,,Number of processes: There must be at least as many processes as the
total of configured non-dialog work processes on this instance (
also see Note 934109).
,,If a J2EE instance (dual-stack instance) exists, the minimum number of
DIA processes must be 5.
,,Number of update servers: The update must occur on at least one
,,Release 2.1 and 2.2 :
,,Only configurations with exactly one update server in the system are
officially supported. The name of this server is defined by the
system parameter rdisp/vbname. At least one UPD process must run on this
,,In Releases 2.1 and 2.2, several update servers should be used only if
absolutely necessary (performance). The parameter rdisp/vbname
defines for each server where the update requests must be sent. At
least one update process must run on each of these update servers.
Also refer to Note 7209.
,,The following applies to Release 3.0:
,,Several update servers are allowed. There must be at least one update
process somewhere in the system. The assignment is not carried
out via rdisp/vbname, but is carried out dynamically.
,,If several code pages are used at the same time in one system, there
are further restrictions (see the notes under the key word "MNLS
,,UP2 (update V2 - as of Release 3.0):
,,If there are UP2 processes in the system, a V2 update (an update with
low priority) is possible only in these processes; the UPD proc
esses are then reserved for V1 (an update with high priority).
,,If there are no UP2 processes, the UPD processes take over both V1 and
,,As a result, UP2 processes do not have to exist. However, the V1
update may be delayed if there are no UP2 processes. If you decide t
o configure UP2 on an instance, we recommend that you define at least
TWO UP2 on such an instance.
,,Number of processes: at least 1 in each system, at least 2 during the
,,Reservation of processes for job class A:
,,If n background processes are running, a maximum of n-1 processes may
be reserved for class A jobs. Otherwise, jobs with class B and
C would be blocked (see Note 36280).
,,Number of servers: there is exactly one enqueue server in the system
(system parameter rdisp/enqname)
,,Number of processes: One ENQ process must run on the enqueue server.
It may make sense only in certain special cases (extremely large
systems) to have more than one ENQ process running (on the same
,,Number of processes per system: as many as required, at least 1
,,Number of processes per server:
,,The following applies to 2.x/3.x releases: a maximum of 1
,,The following applies to Release 4.0A and above: as many as required
,,See Note 108799 to decide how many spool work processes should be
,,Spool processes cannot be switched on and off when switching between
,,The following applies to releases up to and including Release 2.1J and
2.2D: If several servers of the same system are installed on t
he same host, one spool work process may run on a maximum of one of
,,The following theoretical minimum configurations result from the above
,,for a central system: 5 DIA, 1 UPD, 0 UP2, 1 BTC, 1 ENQ, 1 SPO
,,for a dialog server: 2 DIA, 0 UPD, 0 UP2, 0 BTC, 0 ENQ, 0 SPO
How many work processes are useful?
,,If there are too few processes of one type...
,,... requests (dialog steps, updates, background jobs) must wait for
free work processes. Ideally, you should use a configuration in w
hich at least one work process is always free.
,,Kernel releases UP TO BUT NOT INCLUDING 720:
,,When you use transaction SM50, you will see that the dialog work
process with the highest number uses almost no CPU time.
,,Kernel release FROM AND INCLUDING 720:
,,Requests are distributed more or less evenly, so the CPU time in
transaction SM50 is no longer conclusive. However, you can use the s
erver information queue information in the SM51 "Goto" menu to determine
the maximum number of requests in the DIA queue since the ins
tance start. A large number of requests denotes a temporary "traffic
jam". The performance of the computer dictates what value is actu
ally considered to be a large number of requests. You can find more
information about the periods for which there was a high value in
"dev_disp". See SAP Note 1148690. (Similarly: If someone wants to
telephone from A to B, they do not want to wait. Therefore, the line
s should never be 100% busy.)
,,If too many processes are configured...
,,... only swap space is consumed, and the system may become slightly
slower due to operating system paging. Therefore, if you have lim
ited main memory resources and the machine is heavily loaded, it may
make sense to use a relatively small number of processes. Dialog
users or background jobs will then have to wait for free processes, but
that is less critical compared to the entire system slowing do
wn. For more information, see Note 9942.
,,If the machine is very powerful...
,,... it may make sense, to install several instances (see Note 21960)
or to change over to a 64-bit operating system (an even better s
,,Since the requirements for a server may vary, it often makes sense to
define different operation modes for the entire system.
,,Example: Daytime operation - many dialog processes; Nighttime
operation - many background processes
,,The total number of work processes (DIA+UPD+UP2+BTC+ENQ+SPO) must not
change during the switch; this applies to each server. The numb
er of spool processes (SPO) must also remain constant.
How do I see which work processes exist and what they do?
,,Tools -> Administration -> Monitor -> System Monitoring -> Process
Overview (transaction SM50)
,,Tools -> Administration -> Monitor -> System Monitoring -> Servers ->
<(><<)>Double-click> (transaction SM51)
,,Tools -> Administration -> Computing Center -> Management System ->
Control -> All Work Processes (transaction SM66, the selection of
processes is adjustable)
To see the utilization of the services (dialog, update), choose the
following: Transaction ST03 - > Performance Database -> Task Type
System parameter setting:
The number of work processes is initially predefined by the following
By defining the operating modes, you can dynamically change the
distribution of work processes to services. The reservation of backgro
und work processes for job class A is also carried out exclusively by
defining the operation mode.
Online documentation is available for the system parameters (see Note
RZ04, RZ10, SM63, SM50, SM51, SM66