gtpi1m4k | System Installation Support Reference |
The select a rapid transport protocol (RTP) connection user exit, URTP,
allows you to specify which RTP connection to use when an LU-LU session is
started. You can start a new RTP connection for the LU-LU session or
you can choose an existing RTP connection.
URTP is called only when the following conditions are true:
- An LU-LU session is being started.
- High-performance routing (HPR) support is enabled in the TPF
system.
- The primary logical unit (PLU) resides in the TPF system.
- Part or all of the route calculated for this LU-LU session supports HPR
support.
- One or more RTP connections that can be used for this LU-LU session
already exist.
Input
- EBX016-EBX019
- Address of the parameter list, which contains the following:
- Bytes 0-3
- Number of existing RTP connections that can be used for the LU-LU
session.
- Bytes 4-n
- An 8-byte entry for each RTP connection that can be used, which contains
the following:
- Bytes 0-2
- Rapid transport protocol control block (RTPCB) index of the RTP
connection.
- Byte 3
- Status of the RTP connection, which can be the following:
- X'01'
- Starting
- X'02'
- Connected
- X'03'
- Switching
- X'04'
- Moving
- X'05'
- Resynchronizing.
See the IRTP_STATUS field in the IRTPB DSECT for more information.
- Bytes 4-7
- Number of LU-LU sessions currently using the RTP connection.
Programming Considerations
- IBM provides sample code for URTP, which selects the RTP connection that
has the least number of LU-LU sessions. If all of the RTP connections
that can be used have 20 or more LU-LU sessions, the sample code indicates
that a new RTP connection should be started.
- The logic for sending output messages processes each RTP connection
equally, regardless of the number of LU-LU sessions using each RTP
connection. For example, if one RTP connection has 100 LU-LU sessions
and another RTP connection has 5 LU-LU sessions, both of these RTP connections
are processed equally. Therefore, try to distribute traffic equally
over RTP connections.
- Data levels D0 and D4 must not be modified. All other data levels
can be used by this user exit.
- EBW000-EBW103 and EBX000-EBX103 must not be modified.
- See TPF ACF/SNA Data Communications Reference
for more information about HPR support.
Return Values
R0 contains the return code:
- 0
- Start a new RTP connection.
- x
- The RTPCB index of the RTP connection to be used.