Tuxedo, TMS, threads and X/Open RMs

Question

Hi!
I would be very interested in knowing how Tuxedo manages Xids when connecting to an external Resource Manager. Essentially I am trying to create an X/Open DTP compliant Resource Manager to an external System, using the Tuxedo option of creating a shared library under Solaris, with a linkable xa_switch structure.
In association with this effort I have been told that at least two TMSes have to be configured/built on the Tuxedo side and that these TMSes will use the RM in a threaded manner. This would mean that they would share transactions in a losely coupled way: that is the threads will use different Xids, but access the same transaction in parallel. This would lead to the assumption that one would need to synchronize access to the transaction - typically by using mutexes.
My question is simple: if the TMS threads se different XIDs - how is the RM to identify the fact that they are using the same global transaction?
Would the treads use the same global transaction identifier, but different branch transaction identifier, perhaps? This would explain one thing or two.
Any insight would be very much appreciated!
Kind Regards

Answer 1

Johan,
Tuxedo does make use of branch IDs when passing XIDs to a resource manager.
Within any particular group, the same branch ID is used for all application
servers and TMS servers within that group, which means that Resource Manager
locks can be shared between the servers in a group. (There need to be at
least 2 TMS servers per group because certain XA operations can block in the
RM, and one TMS needs to be dedicated to performing only nonblocking XA
operations in order to avoid deadlocks.)
A different branchID is used for each Tuxedo group in which work is
performed for a particular global transaction identifier. This means that
if the same RM is associated with two different Tuxedo groups, a server in
one group may not be able to share database locks with a server operating on
the same transaction in another group, which can lead to deadlocks in some
cases. (Usually, all of the servers associated with a particular database
are in one group and different groups are used for different RMs. Multiple
groups per RM can be used, but then there is loose coupling and two groups
may need to be involved at commit time instead of one.)
Tuxedo does need to lock its global transaction table for brief periods
during transaction processing to update shared data, but locks on this table
are not held throughout a transaction. Resource managers do need to lock
data that has been updated during a transaction until the transaction is
committed or rolled back, and some resource manager consistency levels will
also lock data that has been read for the duration of the transaction.
Ed
<Johan Hellstrom> wrote in message news:[email protected]...
Hi!
I would be very interested in knowing how Tuxedo manages Xids when
connecting to an external Resource Manager. Essentially I am trying to
create an X/Open DTP compliant Resource Manager to an external System,
using the Tuxedo option of creating a shared library under Solaris, with a
linkable xa_switch structure.
In association with this effort I have been told that at least two TMSes
have to be configured/built on the Tuxedo side and that these TMSes will
use the RM in a threaded manner. This would mean that they would share
transactions in a losely coupled way: that is the threads will use
different Xids, but access the same transaction in parallel. This would
lead to the assumption that one would need to synchronize access to the
transaction - typically by using mutexes.
My question is simple: if the TMS threads se different XIDs - how is the
RM to identify the fact that they are using the same global transaction?
Would the treads use the same global transaction identifier, but different
branch transaction identifier, perhaps? This would explain one thing or
two.
Any insight would be very much appreciated!
Kind Regards