Each IUCV link must be defined with a LINK statement. LINK statements must follow the related DRIVER statement. The following is an example of the IUCV LINK statement:
For more information about syntax conventions and rules used in this document, read Conventions.
The LINK statement parameters are read from a sequential file during system startup. Some of the parameters can be modified after startup using the ALTER operator command. See the ALTER operator command in the section IUCV Operator Commands . The parameters that can be modified using ALTER are identified in the following descriptions.
The USERID parameter is required. All other parameters are optional and have default values as described. The underlined portion of the parameter is the minimum abbreviation.
BLOCKMSG={Y | N}
The default BLOCKMSG=Y (Yes) causes messages for this link to be blocked for transmission. If N (No) is specified, no blocking occurs.
GLTIME={secs | 60}
This optional parameter specifies the maximum elapsed time in timer units (one unit = 1.05 seconds) allowed for a request over a group link to be completed. Accepted values range from 1 to 2147483647 (approximately 68 years; effectively, no timeout occurs). The default is 60 (approximately one minute).
MAXBLK=block-size
This optional parameter specifies the maximum transmission block size for the link. The value block-size can be up to 9 decimal digits in length. There is no default size; if no value is specified, no limit is set for the size of a transmission block. For group links between guest operating systems and other systems or users/targets, this value is replaced by the block size appropriate for the guest operating system, and must be a multiple of 2048 bytes. For direct links between virtual machines, both ends must specify the same block size, or errors may occur. If no value is specified, and the environment limits the transmission block size to a page, the parameter will be set automatically to the proper value. Specifying a value smaller than needed will influence the performance negatively.
MSGLIM=n
This optional parameter specifies the maximum number of outstanding IUCV messages allowed on this link. If the MSGLIMIT option was specified in the CP directory, this parameter can be used to decrease the value in the directory, but the directory value will override any larger value specified in the MSGLIM parameter. To allow for maximum flexibility, it is recommended that the MSGLIMIT option not be specified in the CP directory.
The value for the MSGLIM parameter can be 1-255. If not specified, MSGLIM is set to the value of the MSGLIMIT option. If no MSGLIMIT option is specified, MSGLIM is set to ten (10).
PSTATS={N | Y}
This optional parameter determines whether or not (Y or N) statistics are printed to DDPRINT when the statistics interval expires. The default value is PSTATS=Y. This parameter does not affect the STATS operator command. The PSTATS parameter can be modified with the ALTER operator command; the link may be open or closed.
RESID=resource-id
This parameter is the IUCV resource ID for the Entire Net-Work IUCV line driver. The resource ID is a logical name for an IUCV service. The standard resource ID for Entire Net-Work is SAGNETWK. This parameter should be issued only when it is necessary to run two separate versions of Entire Net-Work with IUCV line drivers concurrently. An example for this could be a test and a production network. If specified, the resource ID should be the same on all nodes.
The RESID specified on the LINK statement must have the same value as the RESID parameter specified on the DRIVER statements of other nodes that are to be connected to this node.
RESTART=retry interval and number retries (i,n)
RESTART specifies the retry interval in seconds (i) and the number of retries (n) to be used if you want Entire Net-Work to attempt to reconnect the link following a shutdown due to a failure. If RESTART is not specified or (i) is specified as zero, no retry is attempted. By specifying (n) as zero, an infinite number of retries can be requested.
The TIMER parameter on the NODE statement affects the RESTART parameter. (See the section Entire Net-Work NODE Statement .) The retry interval should not be less than the TIMER parameter, and should be a multiple of this value. If a retry interval other than zero is specified that is less than the value of the TIMER parameter, the TIMER value is used instead. The RESTART parameter can be modified with the ALTER operator command; the link may be open or closed.
If a RESTART interval and count are also specified for the IUCV DRIVER statement, it is recommended that the LINK restart interval and retry count be coordinated with those values to ensure that a link restart follows an IUCV driver restart, if it occurs.
RSTATS={N | Y}
This optional parameter determines whether or not (Y or N) statistics are automatically reset when the statistics interval expires. The default value is N. The RSTATS parameter can be modified with the ALTER operator command; the link may be open or closed.
STATBLK={N | Y}
This optional parameter specifies whether or not blocking statistics for the link are created. For this parameter to take effect, the BLOCKMSG parameter must also specify Y (Yes). The STATBLK parameter can be modified with the ALTER operator command; the link may be open or closed.
Blocking statistics are kept for
the number of messages blocked into transmission blocks;
the number of transmission blocks created;
the number of messages rejected for lack of block space ("thrown back"); and
the maximum number of messages "thrown back" for any given block.
STATINT={statistics interval | 3600}
This optional parameter specifies the amount of time, in seconds, before statistics are automatically printed or reset. The default is 3600. A value of 0 is reset to 3600. The STATINT parameter can be modified with the ALTER operator command; the link may be open or closed.
TYPE={1WAY | 2WAY}
This optional parameter specifies whether the IUCV protocol SEND/REPLY (SEND 2WAY) or the SEND 1WAY is to be used. The default is SEND/REPLY (2WAY). For more information about the appropriate protocol, see the section Factors Affecting Compatibility and Performance.
USERID=vm-user-id
This parameter specifies the z/VM user ID (VMID) of the target virtual machine. This parameter must be specified; there is no default user ID.
WEIGHT={n | 256}
This parameter allows a performance- or cost-based value to be assigned to each link in order to provide Entire Net-Work with information on which to base path selection if more than one path to a destination is available. A higher value should be used for faster, more expensive links, and a lower value for slower links. The default value is WEIGHT=256.