INET Command: Manipulate TCP/IP Attributes

Commands › INET Command: Manipulate TCP/IP Attributes

INET Command: Manipulate TCP/IP Attributes

To display and manipulate TCP/IP attributes, use the INET command.

Authority: To issue the INET command, you require OPER authority.

This command has the following format:

INET {DISPLAY} {ACTIVE}
               {CLOSE}
               {HOST_CACHE}
               {TCPIP}
               {TRACE}
               {BIND}
	    {FLUSH HOST_CACHE}
     {HELP}
     {PURGE {ID socketid|TASK taskid}}
     {QUERY HOST hostname}
     {SET} {TRACE} SYSOUT(class)
           {CLOSE {RESET|SHUTDOWN}}
           {HOST_CACHE TTL(seconds)}
           {BIND {REUSEADDR|NOREUSEADDR}}
     {SPIN} {TRACE}
     {START}{TRACE}
     {STOP} {TRACE}

DISPLAY

Displays a TCP/IP object. The following options are supported:

INET DISPLAY ACTIVE
CLOSE
INET DISPLAY HOST_CACHE
INET DISPLAY TCPIP
INET DISPLAY TRACE
INET DISPLAY BIND

ACTIVE

Displays all active TCP/IP sockets.

CLOSE

Displays the current TCP/IP close option (RESET or SHUTDOWN).

HOST_CACHE

Displays z/OS Agent TCP/IP host cache entries.

TCPIP

Displays information on the current TCP/IP stack.

TRACE

Displays TCP/IP tracing facility.

BIND

Displays the current TCP/IP bind.

FLUSH HOST_CACHE

Flushes z/OS Agent TCP/IP host cache. Flushing is useful when a host cache entry has become invalid because of a modification to a host entry in the TCP/IP network Domain Name System (DNS) configuration.

HELP

Displays all the INET command options.

PURGE

Purges a TCP/IP socket or all TCP/IP sockets running under a specified task.

ID

Requests the purging of an active socket.

Note: This option is not supported if the TCP/IP stack is IUCV from IBM.

socketid

Displays a list of currently active TCP/IP sockets.

TASK

Displays a list of currently active TCP/IP sockets and their respective task IDs.

taskid

Displays a list of currently active TCP/IP sockets and their respective task IDs.

QUERY HOST hostname

Displays the TCP/IP address of a host. The short form is: INET Q H hostname.

SET

Sets a TCP/IP object.

SYSOUT(class)

Indicates a print data set for the TRACE log SYSOUT.

CLOSE

Use this operand only under the direction of CA Support. CLOSE tells z/OS Agent how to close a TCP/IP connection, either gracefully (SHUTDOWN) or forcefully (RESET). The default is SHUTDOWN.

HOST_CACHE TTL(seconds)

Activates or de-activates TCP/IP host caching, or resets the time-to-live (TTL) interval. Seconds is the time-to-live value within the range 0-99999999. A value of 0 de-activates TCP/IP host caching.

BIND {REUSEADDR|NOREUSEADDR}

Sets the TCP/IP bind option. When you use REUSEADDR, the TCP/IP bind does not fail if TCP/IP connection sockets are active using the requested TCP/IP port.

Note: If another listener socket is bound to the requested port, the TCP/IP bind always fails.

SPIN

Spins a TCP/IP object. Currently the only supported option is INET SPIN TRACE.

The TCP/IP trace sysout file is closed and deallocated. A new one is then immediately allocated and opened.

START

Starts a TCP/IP object. Currently the only supported option is INET START TRACE.

A TCP/IP trace sysout file is allocated and opened. Before the TCP/IP trace file can be started, it must be set to a sysout class by the INET SET TRACE SYSOUT(class) command.

STOP

Stops a TCP/IP object. Currently the only supported option is INET STOP TRACE.

The TCP/IP trace file is closed and de-allocated.

A DNS host name or IP address identifies z/OS Agent. If you use the host name, z/OS Agent converts it to an IP address before connecting. By default, the GetHostByName lookup routine does the connection.

z/OS Agent exploits the TCP/IP host caching mechanism to perform the host name to the IP address lookup process. When activated the first time:

A lookup is done for a given host.
A memory host cache entry is created.
The GetHostByName lookup is performed.

z/OS Agent maintains a memory cache of a host name and the corresponding IP address after the first DNS lookup. The cache is used for subsequent lookups, sparing the overhead of unnecessary DNS lookups.

If you frequently use the same set of host names, activating host caching minimizes the number of real DNS lookups.

Host caching significantly improves z/OS Agent TCP/IP performance when:

Scheduling managers are identified to z/OS Agent by host names rather than IP dotted decimal address.
Connections are frequent.
TCP/IP name server resides on a different system from z/OS Agent.

Example: List INET Options

This example shows how to display all of the INET command operands.

INET HELP

Example: Display TCP/IP Sockets

This example shows how to display all active TCP/IP sockets.

INET DISPLAY ACTIVE

Example: Purge All Sockets

This example shows how to purge all TCP/IP sockets running under task ID 78E0.

INET PURGE TASK 78E0

Example: Activate Host Caching

This example shows how to use the short form of the INET SET HOST_CACHE command to activate TCP/IP host caching. This command also sets the TTL interval for each host cache entry to one hour.

INET T HC TTL(3600)

Example: Deactivate Host Caching

This example shows how to use the short form of the INET SET HOST_CACHE command to deactivate TCP/IP host caching.

INET T HC TTL(0)