Johnson Controls P2000 Configuration page 85

I M P O R T A N T N O T E S
Initialization
Execution of the snapshot agent places exclusive locks on the target tables as well as
some of the system tables used to manage the replication process. If multiple
snapshots are running simultaneously against the same database, a deadlock can
cause a failure in generating the snapshot. The snapshots are currently configured
not to start immediately. Each snapshot agent must be started by an operator.
Automatic, timed snapshot starts will be added.
Deadlocks and Retries
When a deadlock occurs, one process or job gets aborted. All changes are supposed
to be rolled back in a transaction. Frequently, not all the changes are reversed. This
applies to both the initial snapshot generation and the Subscriber initialization where
the snapshot is applied. The Subscriber initialization is far more sensitive and prone
to problems. In particular, the Subscriber table holding replication identity ranges
and the replication identity constraint on some merged tables do not get cleaned up.
Identity Columns
Identity columns are managed by assigning value ranges to each Subscriber. As a
value range is used up, a new one is assigned. Current range values available for
each article (published table) are kept on the distribution database on the Publisher
in the MSrepl_identity_range table. Additionally, the MSrepl_identity_range table
in the subscribing database contains current range assignments for that database.
Primary Key Violation
The primary key in the MSrepl_identity_range table (in the subscribing database) is
an object id assigned to specific articles. If a process is aborted, this table is not
always cleared out. A second (and every subsequent) attempt by the merge agent to
initialize will generate a Primary Key Violation for this table. Recommended
recourse is to drop the subscription and re-create it.
24-10515-21 Rev. –
This document contains confidential and proprietary information of Johnson Controls, Inc.
© 2010 Johnson Controls, Inc.
B
Appendix
B-1