Data Is Not Being Delivered to Subscribers
·
The data is not being applied due to filtering,
an agent issue, or another replication error.
·
The data is being deleted at the Subscriber
after it has been applied.
There are a number of possible causes for data not being delivered to
Subscribers:
·
The table is filtered, and there are no changes
to deliver to a given Subscriber.
·
One or more agents are not running or are
failing with an error.
·
A transactional subscription was initialized
without a snapshot, and changes have occurred on the Publisher since the
publication was created.
·
Replication of stored procedure execution for a
transactional publication produces different results at the Subscriber.
·
The INSERT stored procedure used by a
transactional article includes a condition that is not met.
·
Data is deleted by a user, a replication script,
or another application.
·
Data is deleted by a trigger, or a trigger
includes a ROLLBACK statement.
Data at the Publisher and Subscriber Do Not Match
Data at the Publisher and Subscriber is considered non-convergent (in other
words the data does not match) if:
·
There are a different number of rows at the
Subscriber than at the Publisher, and the publication is not filtered. If the
publication is filtered, it might be expected that the number of rows differs.
·
The data in one or more rows is different in
content at the Publisher and Subscriber.
Data at the Publisher and Subscriber can be non-convergent for a number of
reasons:
·
Data is updated at a Subscriber that should be
treated as read-only. The subscription database should be treated as read-only
unless you are using merge replication, transactional replication with
updatable subscriptions, or peer-to-peer transactional replication.
·
Triggers are used at the Subscriber. Triggers
can modify data at the Subscriber and also prevent the data from being updated
if the trigger issues a ROLLBACK.
·
Scripts are executed by replication at the
Subscriber but not at the Publisher.
·
Replication of stored procedure execution for a
transactional publication produces different results at the Subscriber.
·
Constraint violations or other issues prevent
rows from being inserted, updated, or deleted at the Subscriber.
The System Has a Performance Issue
Replication performance can be measured along the following five dimensions:
·
Latency: the amount of time it takes for a data
change to be propagated between nodes in a replication topology.
·
Throughput: the amount of replication activity
(measured in commands delivered over a period of time) a system can sustain
over time.
·
Concurrency: the number of replication processes
that can operate on a system simultaneously.
·
Duration of synchronization: how long it takes a
given synchronization to complete.
·
Resource consumption: hardware and network
resources used as a result of replication processing.
Replication performance is affected by the following factors:
·
Server and network hardware
·
Database design
·
Distributor configuration
·
Publication design and options
·
Filter design and use
·
Subscription options
·
Snapshot options
·
Agent parameters
·
Maintenance
A Slow Network Is Causing Problems
Security Issues Are Preventing Data from Being Replicated
The password has changed for an
account used by one or more replication agents.
An account used by a replication
agent is no longer valid and must be changed.
A replication agent does not have
sufficient permissions to connect to a computer in the topology or perform
operations in a database.
The Snapshot Agent cannot write to
the snapshot folder; the Distribution Agent or Merge Agent cannot read from the
snapshot folder.
Running a Large Number of Agents Is Causing Memory Problems
In
some cases, you might need to run a large number of replication agents
simultaneously on a single computer. For example, if you are generating
snapshots for a large number of publications or you are synchronizing a large
number of push subscriptions at the Distributor. In these situations, the
non-interactive desktop heap (a memory structure in Microsoft Windows) can run
out of memory.