TMA SNA supports full high availability connection between Oracle Tuxedo and CICS, with no single point failure. Both bidirectional load balancing and bidirectional failover are supported.
This chapter discusses the following topics:
One Tuxedo client calls a remote service, which maps to a CICS DPL program. The DPL program runs in two CICS regions – CICSA and CICSB. Meanwhile, two GWSNAX/CRM pairs are configured to avoid any single point of failure. Each CRM connects to both CICS regions.
In this sample, there are four types of call paths:
Client -> SNAX11 -> CRM1 -> CICSA
Client -> SNAX11 -> CRM1 -> CICSB
Client -> SNAX12 -> CRM2 -> CICSA
Client -> SNAX12 -> CRM2 -> CICSB
Load balancing from Client to GWSNAX follows Oracle Tuxedo load balancing behavior. Load balancing from CRM to CICS is round robin.
One CICS transaction links a remote program via DPL call, which maps to an OracleTuxedo service. The Tuxedo service is provided by two Tuxedo servers reside separately on two Tuxedo domains – TUX1
and TUX2
. Meanwhile, two GWSNAX/CRM pairs are configured to avoid any single point of failure.
The load balancing (round-robin) / failover can be accomplished via following 2 call paths:
DPLC -> CRM1 -> SNAX11 -> Server
DPLC -> CRM2 -> SNAX21 -> Server
Dynamic routing can be configured in CICS to dispatch the request to two CRMs with load balance and failover automatically, and the default dynamic routing program, DFHDYP
, should be customized accordingly.
DFHDYP
is a CICS-supplied, user-replaceable program for dynamic routing; (you can use the default program as a model and write your own program). For eligible DPL requests, it is invoked before a linked program is executed, to obtain the SYSID
of the region where the link should be routed. For more information, see IBM (CICS Intercommunication Guide).
The term connection is used for the TCP connection between GWSNAX and CRM, and the term link is used for the SNA connection between CRM and CICS. TMA SNA supports both multiple connections and multiple links simultaneously.
Note: | GWSNAXs connect to one CRM must be in different Tuxedo domains. |