MAXDATA

For PU type 1:


   .-MAXDATA--=--261-------------.   
>>-+-----------------------------+-----------------------------><
   '-MAXDATA--=--number_of_bytes-'

statements:

dependency:

none

range:

20-65535

For PU type 2:


   .-MAXDATA--=--265-------------.   
>>-+-----------------------------+-----------------------------><
   '-MAXDATA--=--number_of_bytes-'

statements:

dependency:

none

range:

20-65535

Specifies the maximum number of bytes that the physical unit can receive in one PIU or PIU segment, including the transmission header (TH) and request or response header (RH). To determine the maximum PIU (or PIU segment) size that the physical unit can receive, consult the component publications for the specific type of SDLC station represented by this PU definition statement.

The maximum amount of user data that VTAM® sends to the physical unit in one PIU is:

MAXDATA minus 2 bytes (for a PU type 1)
MAXDATA minus 6 bytes (for a PU type 2)

Note: The RU part of the PIU contains the user data. When VTAM segments the PIU, the middle and last PIUs contain three more bytes of user data in the RU because there is no RH field. The value for the PIU varies with the device; for example, the 3276 requires MAXDATA=262.

MAXDATA is ignored for type 2.1 nodes attached through an NCP with peripheral node type 2.1 support. The type 2.1 node supplies the actual value used when the connection is established.

See NCP, SSP, and EP Resource Definition Reference for more information about physical units connected through an NCP.

Note: If the TRLE operand is coded, MAXDATA is ignored. See TRLE for more information.

Note:

In a local area network, the value for the MAXDATA operand on the PU definition statement must be less than or equal to the value for the MAXDATA operand on the PORT definition statement for the LAN major node to which the switched physical unit is connected.
NCP V4R3 changed the MAXDATA calculation for a type 1 physical unit. See NCP, SSP, and EP Resource Definition Reference for information about calculating a MAXDATA value for physical units on non-switched links.