IBM AS/400E Step 2ASCIISetting the Number of Virtual Devices, Security Considerations for ASCII Full-Screen Mode

Step 2—ASCII—Setting the Number of Virtual Devices

Virtual devices are used by the server system to direct output to devices on your

system. AS/400 Telnetserver support automatically selects (and creates, if

necessary) these devices for you. Youmay also choose to create your own virtual

device under the QVIRCDnnnn virtual controller.

The option is available for you to allow the Telnetserver support on the AS/400

system to automatically conﬁgure virtual controllers and devices. The QAUTOVRT

system value speciﬁes the maximum number of devices that are automatically

conﬁgured by the system. Use the Change System Value (CHGSYSVAL)command

to change the value of the QAUTOVRT system value. For example, entering the

following command string changes the number of virtual devices that can be

allocated on a system to 50:

CHGSYSVAL SYSVAL(QAUTOVRT) VALUE(50)

Note: QAUTOVRT has been modiﬁed for Version4 Release 2 to support numeric

values of 0 through 32500, and a special value of *NOMAX.

Todetermine and set the maximum number of users you want signed on to the

AS/400 system at any time, do the following:

1. Set the QAUTOVRT value to 32500, the maximum value allowed, or use the

*NOMAX value.

2. Let your users use pass-through, Telnet,and the virtual terminal application

program interface until you decide that the number of virtual devices created is

sufficient for normal system operation.

3. Change the QAUTOVRT value from 32500 to the number of virtual devices you

require for normal system operation.

If you have never allowed automatic conﬁguration of virtual devices on your system,

the QAUTOVRT value is 0.A Telnet connection attempt with a dependence on

automatic creation of the virtual device then fails because the Telnetserver does

not create more than the speciﬁed QAUTOVRT devices (zero). If you try to connect,

you receive a message (TCP2504) indicating that the Telnetclient session has

ended and the connection is closed. In addition, the QTGTELNETS job in the

QSYSWRK subsystem on the AS/400 Telnetserver sends a message (CPF8940)

indicating that a virtual device cannot be automatically selected.

If you change the QAUTOVRT value to 10, the next Telnetconnection attempt

causes the Telnetserver to create a virtual device. This virtual device is created

because the number of virtual devices on the controller (0) is less than the number

speciﬁed in the QAUTOVRT (10). Even if you change the speciﬁed number to 0

again, the next user attempting a Telnetconnection succeeds. When a Telnet

connection attempt fails, the CPF87D7 message is sent to the system operator

message queue on the Telnetserver system. The CPF87D7 message indicates that

the AS/400 server is not able to create a virtual device.

Security Considerations for ASCII Full-Screen Mode

The number of sign-on attempts allowed increases if virtual devices are

automatically conﬁgured. The number of sign-on attempts is equal to the number of

system sign-on attempts allowed multiplied by the number of virtual devices that

can be created. The number of system sign-on attempts allowed is deﬁned by the

QMAXSIGN system value. The number of virtual devices that can be created is

deﬁned by the QAUTOVRT system value.

212 OS/400 TCP/IPConﬁguration and Reference V4R4