Types of Buffer Pools

All buffer pools are allocated in extended CSA subpool 231 with KEY=6.

APBUF

Used to provide fixed common storage if VTAM fails to obtain other storage from the operating system. For buffers not related to I/O.

BSBUF

Used to maintain session information for peripheral nodes for which VTAM performs boundary function. One buffer is required for each boundary LU session (SSCP-PU, SSCP-LU, LU-LU).

CRA4

Used for scheduling and error recovery.

CRA8

Used for scheduling and error recovery.

CRPLBUF

RPL-copy pool. One buffer is required for each VTAM application program request until the operation is complete.

IOBUF

Used for input/output data. Every PIU that enters or leaves VTAM resides in an I/O buffer. This pool is 31-bit addressable.

LFBUF

One buffer is required for each active application program with an EAS value (on APPL definition statement) less than 30. If the EAS value is greater than 30, this information is contained in SFBUF. One buffer is required for each TSO user who is logged on.

LPBUF

Used for scheduling and audit trail (error recovery). One buffer is required for each active VTAM process.

SFBUF

Used to contain application program information and LU blocks. One buffer is required for each active application program with an EAS value (on APPL definition statement) greater than or equal to 30.

SPBUF

Used for large message (LMPEO) requests. One buffer is required per concurrent LMPEO send request.

TIBUF

Used to perform input/output operations for CSM-capable protocols. This pool is in 31-bit storage.

XDBUF

Used for physical I/O to VTAM peripheral nodes for connection activation (for example, XID exchange processing). This pool is 31-bit addressable.

The buffer pool types specifically used by TCP/IP are: IOBUF, LFBUF, CRPLBUF, TIBUF, and CRA4.

See also: