01.08.2008 Page 1 of 4

Note 108799 - How many spool work processes for each instance?

Note Language: English Version: 6 Validity: Valid from 17.03.2000

Summary

SymptomAs of Release 4.0A, you can configure more than one spool work process foreach instance. During the configuration of the R/3 server landscape, thequestion arises as to how many spool work processes should be configuredfor each server.

Additional key wordsReservation of spool work processes, order processing in accordance withthe set sequence

Cause and prerequisites

SolutionThe spool work processes have different tasks: Up to (exclusively) 4.0A,the spool work process is responsible for processing print requests andtransferring them to a host spool system. Furthermore it is responsible fordemanding the job statuses in the host spool systems and scanning the spooldatabase for requests lost through queue overflows. In Release 4.0A, it isalso in charge of reassigning output requests during a spool servershutdown. In addition, a separate (printer-independent) link check for hostspool systems (access method U and S) is carried out in Release 4.0B.As of Release 4.6A, a spool work process also conducts the deletion ofobsolete spool requests (as an option, you can configure this inTransaction SPAD via spool-settings).

Thus, the tasks of a spool service can be divided into three classes:

o Processing of output requests

o Local management actions

- Requesting the host spool

- Link check

o Global management actions

- Scanning for lost requests

- Reassigning requests

- Deleting obsolete requests

The global management tasks are carried out throughout the system by amaximum of one spool work process. In the case of several configured spoolwork processes, the local management tasks are carried out for eachinstance exclusively by one spool work process. As a result, the spoolservice of an instance cannot be blocked by parallel processing of the samemanagement tasks. In this way the spool service cannot, for example, becrippled by hanging or lengthy host spool demands if a minimum of two spoolwork processes is configured. Only the further demand is delayed until thecurrent demand process is completed.

01.08.2008 Page 2 of 4

Note 108799 - How many spool work processes for each instance?

Configure one spool work process more on a spool server than there areparallel management tasks. This way, the server can process output requestseven in the case of maximum load with all management tasks. As of Release4.0B, for example, at least one spool work process out of four is availablefor the exclusive processing of output requests:

o a maximum of one work process for global management tasks

o a maximum of 2 work processes for local management tasks

- a maximum of one work process for the host spool demand

- a maximum of one work process for the link check

o and a minimum of one work process for output

As of Release 4.6A, frontend print requests are no longer processed by thespool service via dialog work processes. As a result an additional spoolservice load arises. By default the number of spool work processes usefulfor the frontend print is limited to 1 (can be changed via the profileparameter rdisp/wp_no_spo_Fro_max). To have the same service available toprocess the usual output requests, as existed prior to Release 4.6A, thenumber of spool work processes must be raised by 1 (or the value of theprofile parameter rdisp/wp_no_spo_Fro_max). As a result at least one spoolwork process is exclusively available to process output requests as of 5work processes.

o a maximum of 1 work process for global task management

o a maximum of 2 work processes for local task management

- a maximum of 1 work process for host spool demand

- a maximum of 1 work process for the link check

o and a minimum of 2 work processes for the output

- a maximum of 1 work process for frontend output requests

- and a minimum of 1 work process for outputting normal requests

The following information will help you avoid misunderstandings: Of courseoutputting may occur with fewer spool work processes. The examples usedhere only illustrate as of how many work processes at least one spool workprocess can process output requests. Because the management tasks do notcome up regularly and must be performed, the spool work processes specifiedin the list are available for the rest of the time to process outputrequests. But even only then if no similar actions are to be executed. Withfewer work processes it may occur that, in extreme cases, no outputrequests may be processed for a certain time. This is only then possible ifat least one of the listed management actions no longer needs a workprocesses owing to the selected interval and the length of the action.

The option of configuring several spool work processes for each instancecauses problems concerning processing of output requests of a device inaccordance with the set sequence. If you want to utilize maximum parallelprocessing, it must also be possible to process several requests of adevice in parallel. However, requests of one device can overtake each other

01.08.2008 Page 3 of 4

Note 108799 - How many spool work processes for each instance?

due to different processing and process assignment times (through theoperating system) so that processing in accordance with a set sequence isno longer possible. This is not always required. Therefore, as of Release4.0A, you must decide separately for each R/3 output device whetherprocessing in accordance with a set sequence is required. When upgrading anolder system, this option is selected automatically to achieve compatiblebehavior. New devices are created by default as not in accordance with aset sequence.

Processing in accordance with the set sequence restricts the possibility tocarry out several processes in parallel. It can only be achieved ifprocessing is still carried out by a maximum of one spool work process.When you process requests for output devices in accordance with a setsequence, work processes are therefore exclusively reserved. Thisreservation is carried out dynamically and does not need a separateconfiguration.Since requests can principally be dealt with by all work processes, aseparate incoming queue is used for every reserved spool work process. If aspool work process receives a request for a device for which a work processhas already been reserved, this request is not edited by the further workprocess, but simply put in its queue. If, on the other hand, no suchreserved spool work process exists, the current process is reserved for thecorresponding device and only processes its own input queue from this timeonwards. Only if all requests in this queue are processed, does itparticipate again in the request dispatching and give up its reservation.

Due to the dynamic reservation it cannot happen that requests to (too many)sequence devices cripple a spool server and that other requests can nolonger be processed since a once-reserved spool work process accepts nomore global requests until its internal queue is processed. However, atthis time its reservation is cancelled again so that it can also processrequests from other devices. If all spool work processes are reserved, nomore requests are distributed to the internal queues so that at least onespool work process must give up its reservation before new requests can bereceived.

Since the requests of a device which follow a set sequence can only beprocessed by one spool work process, a performance bottleneck of a spoolserver caused by an excessively high load cannot be solved by increasingthe number of the spool work processes.The problem can only be solved by not adhering to the sequence. In the caseof devices which follow the sequence, only a performance bottleneck causedby too many requests to different devices can be solved by increasing thework process number.With the dynamic reservation, it is not necessary to increase the number ofspool work processes by changing the setting of the sequence.

Source code corrections

Header DataRelease Status: Released for CustomerReleased on: 16.03.2000 23:00:00Priority: Recommendations/additional infoCategory: Consulting

Main Component BC-CCM-PRN-SPO Spool System

01.08.2008 Page 4 of 4

Note 108799 - How many spool work processes for each instance?

Valid Releases

Software Component Release FromRelease

To Release and Following

SAP_APPL 40 40A 40B XSAP_APPL 45 45A 45B XSAP_APPL 46 46A 46B XSAP_APPL 46C 46C 46C XSAP_BASIS 46 46D 46D XSAP_BASIS 60 610 640 XSAP_BASIS 70 700 700 X

Related Notes

Number Short Text923610 Memory param recommendations for Bank Analyzer 4.2 and 5.0351492 Setting up frontend printing as of Release 4.6B90631 tRFC: all dialog processes are filled65109 Long delays when printing during overload39412 How many work processes to configure