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Chapter 20. TCP/IP Performance
The following are performance items that should be considered when using TCP/IP.
*BASE Pool Size
The TCP/IP protocol and application code always runs in the *BASE pool on the
AS/400 system. If the *BASE pool is not given enough storage, TCP/IP
performance, especially SMTP performance, can be adversely affected.
Although it is possible to run in less than 4000 KB of storage to perform well when
running both FTP and SMTP sessions, it is suggested that the *BASE pool be
configured to use at least 4000 KB of storage. You can use the WRKSYSSTS to
view and change pool sizes on the AS/400 system. Pool 2 is the base pool. Another
alternative is to change the pool in which the TCP/IP jobs run.
TCP/IP Jobs
TCP/IP jobs, like other jobs on your system, are created from job descriptions and
associated classes. The job descriptions and classes should be adequate in most
cases; however, they may be changed to fit your configuration. The TCP/IP job
descriptions, classes, and subsystem descriptions can be found in the QTCP or the
QSYS library that was loaded in your system when TCP/IP was installed.
Each application has a job description associated with it. This job description has a
number of items associated with it that define how the application runs on the
AS/400. One of these pieces of information is the routing entry compare value. This
value identifies which routing entry in a subsystem description is used when this job
is submitted. By changing that routing entry, you can select in which storage pool to
run the jobs for a particular application. For information on compare values, see
Work Management
.
Other items that can be changed or selected on a job description include the job
priority, the logging level for messages, and the initial library list.
If the storage pool that you select to run the TCP/IP application jobs in is not large
enough, excessive paging can occur. This directly affects performance on the
AS/400 and the performance of the applications.
TCP/IP Protocol Support Provided by IOP
AS/400 TCP/IP protocol support runs down in the AS/400 System Licensed Internal
Code, at the same level as LU 6.2 and APPN*. One of the goals of integrating
TCP/IP into the AS/400 System Licensed Internal Code is to provide performance
and capacity comparable to APPC.
Further, moving some functions that are normally done by the TCP/IP software into
the IOP reduces interactions between the system and the input/output processor
(input-output processor (IOP)). These functions may include:
v Checksum calculation of outgoing TCP and UPD datagrams (prior to V4R4)
v Checksum verification of incoming TCP and UPD datagrams (prior to V4R4)
v Outbound batching of TCP and UDP datagrams.
© Copyright IBM Corp. 1997, 1999 425
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