The ADARUN DTP parameter indicates whether or not
a database is capable of full participation in Distributed Transaction
Processing. Normally, when a database is started with
DTP=RM, it is immediately “signed on” to the Transaction
Manager for Distributed Transaction Processing. This means that the Transaction
Manager uses two-phase commit protocol to guarantee the integrity of
distributed transactions that modify this database.
There might be occasions, however, when the process of “signing on” for
DTP cannot be completed immediately, perhaps because of a planned or unplanned
outage of another component that is itself going through startup processing at
the time. During this transient period, Adabas Transaction Manager ensures
uninterrupted operation by treating databases that have not signed on for DTP
as if they were running wth DTP=NO. In these
circumstances, a commit operation is applied to all “unsigned on” databases in
turn immediately after DTP commit has been completed for all databases in the
transaction that are signed on, by means of serial
ET commands. At some later point this transient “not
signed on” period ends because the sign-on eventually succeeds, Adabas
Transaction Manager recognizes the change, and from that point the database is
treated as a DTP=RM database.
In a multi-system environment, it is possible to run completely separate
System Coordinator groups in the separate systems. For example, a “production”
group might run on system A, while a “test” group might run on system B. The
DTP=RM databases used by the “production” environment
would be executing outside the scope of the “test” System Coordinator group. If
an application in the “test” environment modifies a
DTP=RM database in the “production” environment, Adabas
Transaction Manager recognizes that the database is executing outside the scope
of the current System Coordinator group, and it manages the database (for the
“test” client) as if it were running with DTP=NO.
