z/OS Communications Server: SNA Network Implementation Guide
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Improving VTAM performance using the NCPBUFSZ start option

z/OS Communications Server: SNA Network Implementation Guide
SC27-3672-01

To improve performance when you load or dump a link-attached 3720 or 3745 communication controller, you can specify the request unit (RU) size used to transfer either the load module to or the static dump from the communication controller. The default size is 512 bytes, but values of 1024 or 2048 can be specified on the NCPBUFSZ start option to increase buffer size and improve the performance of the load or dump operation.

VTAM® determines the RU size to be used for a dynamic dump. VTAM always attempts to use the 2K transfer for a dynamic dump but uses a 256-byte transfer under any of the following conditions:
  • The SSP does not support a 2K buffer for the transfer operation.
  • The NCP does not support a 2K transfer operation.
  • The lines between VTAM and NCP do not support the use of 2K path information units (PIUs).
Parent topic: Improving VTAM performance using start options

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