User's Manual

Implementing conﬂict resolution

This section describes what you need to do to implement custom conﬂict

resolution in SQL Remote for Adaptive Server Anywhere. The concepts are

the same in SQL Remote for Adaptive Server Enterprise, but the

implementation is different.

SQL Remote allows you to deﬁne conﬂict resolution triggers to handle

UPDATE conﬂicts. Conﬂict resolution triggers are ﬁred only at a

consolidated database, when messages are applied by a remote user. When

an UPDATE conﬂict is detected at a consolidated database, the following

sequence of events takes place.

1. Any conﬂict resolution triggers deﬁned for the operation are ﬁred.

2. The UPDATE takes place.

3. Any actions of the trigger, as well as the UPDATE, are replicated to all

remote databases, including the sender of the message that triggered the

conﬂict.

In general, SQL Remote for Adaptive Server Anywhere does not replicate

the actions of triggers: the trigger is assumed to be present at the remote

database. Conﬂict resolution triggers are ﬁred only at consolidated

databases, and so their actions are replicated to remote databases.

4. At remote databases, no RESOLVE UPDATE triggers are ﬁred when a

message from a consolidated database contains an UPDATE conﬂict.

5. The UPDATE is carried out at the remote databases.

At the end of the process, the data is consistent throughout the setup.

UPDATE conﬂicts cannot happen where data is shared for reading, but each

row (as identiﬁed by its primary key) is updated at only one site. They only

occur when data is being updated at more than one site.

Using conﬂict resolution triggers

This section describes how to use RESOLVE UPDATE, or conﬂict

resolution triggers.

UPDATE statements with

a VERIFY clause

Conﬂict resolution triggers are ﬁred by the failure of values in the VERIFY

clause of an UPDATE statement to match the values in the database before

the update. An UPDATE statement with a VERIFY clause takes the

following form:

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