IBM AS/400E Chapter 20. TCP/IP Performance

Chapter 20. TCP/IP Performance

The following are performance items that should be considered when using TCP/IP.

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. Youcan 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, 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. TheTCP/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 affectsperformance on the

AS/400 and the performance of the applications.

AS/400 TCP/IP protocol support runs down in theAS/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/IPsoftware into

the IOP reduces interactions between the system and the input/output processor

(input-output processor (IOP)). These functions may include:

vChecksum calculation of outgoing TCP and UPD datagrams (prior to V4R4)

vChecksum veriﬁcation of incoming TCP and UPD datagrams (prior to V4R4)

vOutbound batching of TCP and UDP datagrams.