Effects of NCP Parameters
Review the following NCP parameters carefully during the installation:
- BFRS in the BUILD GEN macro that defines the size of NCP buffers
- BFRPAD in the HOST GEN macro that defines the number of pad characters inserted by NCP
- MAXBUFRU in the HOST GEN macro that defines the number of buffers the access method (VTAM) allocates to receive data from the NCP
- UNITSZ in the HOST (VTAM) GEN macro that defines the size of access method buffers used for data transfer from NCP to IBM® Connect:Direct®
- TRANSFR in the LINE or BUILD GEN macro that defines the number of NCP buffers corresponding to the maximum amount of data NCP can receive from another NCP
MAXDATA in the PU unit GEN macro that defines the maximum path information (PIU) size
The following figure illustrates the relationship between these VTAM and NCP parameters. When data is passed from MVS1 to NCPA, the MAXDATA parameter determines the amount of data that NCPA can receive in one segment of a path information unit (PIU).
Between NCPA, NCPB, and NCPC, if you do not specify the TRANSFR parameter on the LINE statement, VTAM searches the BUILD statement. If you do not define TRANSFR on either statement, the default is taken. See the VTAM Customization manual.
When NCPB passes data to MVS2, the MAXBUFRU times the UNITSZ determines the amount of data that can be passed to MVS2. The data cannot exceed the size in bytes of the VTAM IOBUF buffer pool allocation parameters.