39412 SAP OSS Note - How many work processes should be configured?

SAP OSS Note 39412 version 0026 contains details of a know issue related to How many work processes should be configured? . This includes any associated symptoms and instructions on how to fix it, see below for full details. Also check out the comments section to view/add related contributions, questions or screen shots, based on real life experience of this oss note and problem.

...For more information about the SAP support system known as OSS please check out the SAP OSS NOTES SECTION, whih includes how to download & implement them onto your SAP system using transaction code SNOTE.

Note 39412 Details:

When does this problem occur

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


Solution instructions

Definition: In this note, "server" is a synonym for "instance".

Technical conditions:
,,DIA (dialog):
,,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.

,,UPD (update):

,,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.

,,BTC (background):

,,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).

,,ENQ (enqueue):
,,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


,,SPO (spool):

,,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
operation modes.

,,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

these servers.

,,To summarize:

,,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
system parameters:


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


Description of problem

RZ04, RZ10, SM63, SM50, SM51, SM66

Solution instructions

Please import the corrections attached to this OSS note into your SAP system using SNOTE.

You can also view the full details of this OSS note and download it to your SAP system ready for implementation using transaction code SNOTE. Once it has been downloaded you can read the full details, check out any installation instructions including manual changes and see if there are any pre-requisites.

You can also check if a new version of note 39412 has been released as well as see if the note is valid for your current SAP system landscape.

Check if SAP OSS note 39412 has already been downloaded and is valid

To check if this note has already been download, what status it has and if it is valid for your system first execute t-code SNOTE and click on the SAP Note Browser icon
Icon used to execute SAP Note Browser report within SNOTE

From here you can just enter the note number 39412 and press execute. If the note already exists it's details will be displayed. See here for full step by step instructions on how to check if an SAP note has been downloaded and is valid for your system.

If note 39412 does not exist on your system you will receive the message "Unable to find SAP Note that meets specified criteria"
Icon used to execute SAP Note Browser report within SNOTE

If this is the case you will need to download the note to you SAP system also using transaction SNOTE. For further details see Download note using SNOTE. Even if it does exist you may still want to check if you have downloaded the latest version of the note.

Alternatively you can find full details of this note on the SAP service market place(SNumber / Service market place login will be required)