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SAP Note 101717 - Automatic restart of SAP R/3 work processes

Note Language: English Version: 5 Validity: Valid Since 23.11.2001

Summary

Symptom There are memory problems on the database because memory used in a database

transaction are no longer released.

On the database, swaps are executed by the operating system.

Additional key words

Cause and prerequisitesThis generally occurs as a result of a problem in the database or in the

database configuration. The solution described here should only be used if

all other options are exhausted since this is not an elimination of the

actual cause of the problem but only a workaround.

In addition, check SAP settings which have been changed since the problemoccurred even if there is no connection to the database configuration at

first glance.

Solution

With the parameter rdisp/wp_auto_restart, it is possible to restart work

processes periodically for SAP. Here the process is not only restarted but

the corresponding session is also exited in thd database. As a result,

database sessions which have increased unnecessarily as a result of very

large statements are cleared.

An SAP work process checks after each change of the user context whether ithas already exceeded the time interval set. If this is the case, it exits

and the SAP dispatcher starts automatically a new SAP work process. This

then takes over the tasks of its predecessor and processes the ongoing

requests. When changing the user context, all open database operations are

interrupted and all database changes are written to the database by

'commit' even without restart of the work process. Thus, when you restart

the work process after this with the appropriate database connection, this

has no effect on the data consistency.

A restart of the SAP work processes is also triggered automatically if the

memory of the process exceeds a certain limit. As this mechanism does not

consider the memory of the session on the database server, it may be useful

to set the parameter.

Caution:

The parameter may only be set in the instance profiles, but not in

the standard profile (DEFAULT.PFL) since it is unknown there as an

internal parameter.

Restarted SAP work processes are only unavailable for a short

period of time. The contents of the SAP statement cache is lost.

However, this generally only causes insignificant disadvantages.

If the parameter is set on the SAP instance, where the enque workprocess runs, periodic restarts occur as of Release 3.1G (up to and

including version 3.0F only SAP dialog work processes are

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restrated).

If the processing of the enqueue requests is interrupted, the

dispatcher queue may overflow and problems with the lock management

may result. To avoid these problems it is necessary to increase the

number of the enqueue work processes, so that the probability that

a work process is not available is reduced. In addition, increase

the maximum number of entries in the dispatcher queue. Only for the

SAP instance with the enqueue server the following parameters

should be changed in addition to changing rdisp/wp_auto_restart:

- rdisp/wp_no_enq = 3

- rdisp/elem_per_queue = 5000

-

- As from Kernel Release 3.1I, ENQ processes are not restarted so

that a configuration of more than one work process is no longerrequired.

To which value should rdisp/wp_auto_restart be set?

The value of the parameter is entered in seconds.

The time interval depends to a large extent on the size and the utilization

of the system and the perfromance loss which occurs as a result of the loss

the cursor cache for the respective database. This is dependent to a large

extent on the database and the platform. Appropriate settings are between

several days (for example every two days: rdisp/wp_auto_restart 172800) few

hours (for example every three hours: rdisp/wp_auto_restart 10800) up to

half an hour rdisp/wp_auto_restart 1800).

Header Data

Release Status: Released for Customer

Released on: 22.11.2001 23:00:00

Master Language: German

Priority: Recommendations/additional info

Category: Workaround for missing functionality

Primary Component: BC-DB-DBI DB Independent Database Interface

The Note is release-independent

Related Notes

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Number Short Text

789011 FAQ: Oracle memory areas

586824 Restart SAP work processes for BW

502782 Composite SAP Note ora-4030

128221 Increased memory consumption with Oracle >8.0.X

101031 Oracle shadow processes increase continuously

53050 Resetting of SAP Statement Cache

41360 Database configuration using onconfig parameter

38307 Reducing shared memory consumption

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