1. Transactional Replication Deep Dive
Kendal Van Dyke
Senior DBA, Channel Intelligence Inc.
Transactional Replication Deep Dive

2. Agenda General Concepts How It Works Advanced Options Monitoring
Troubleshooting
Q&A

3. General Concepts Publisher Article Publication Subscriber Distributor
Source of data to be replicated to other servers
Article
Table, View, UDF, or Procedure to be replicated
Publication
Collection of articles in a database to be published
Subscriber
Server which receives replicated data
Distributor
Stores all data changes to be replicated between publishers and subscribers in a distribution database
Snapshot
Point-in-time copy of the schema and data for a publication
Agent
Performs replication related tasks (e.g.delivering changes to subscribers)

4. How It Works

5. How It Works

6. Advanced Options Publications
Articles can be configured to determine how they will look at subscribers
Filtering
Articles in a publication can be filtered vertically (columns) and horizontally (rows)
Horizontal filters can include join criteria
Filtering on datetime not recommended – data is not automatically deleted from subscribers
Every transaction must still be examined by Log Reader Agent

7. Advanced Options Publications DDL changes replicated by default
Default synchronization method in 2005 is concurrent
Does not lock tables while taking snapshot
Replicating SPs and UDFs replicates execution. Use snapshot publication to replicate the schema
Replicating Views requires that the base tables exist
Possible to replicate Indexed Views as a table, but not through UI

8. Advanced Options Subscriptions Can be push or pull
Push = distribution agent runs on distributor
Pull = distribution agent runs on subscriber
Subscriptions can be created without synchronization
Use sp_scriptpublicationcustomprocs to generate stored procedures for publication

9. Advanced Options Agents
Use independent agents instead of shared agents for multiple publications on the same publisher
Set agents to run continuously instead of on a schedule
Less latency, less overhead because processes are not stopping\starting constantly
Agent profiles allow each agent to be customized
Distribution Agent
-BcpBatchSize
Number of rows to send in a bulk copy operation (default 1000)
-CommitBatchSize
Number of transactions sent to subscriber before COMMIT (default 100)
-CommitBatchThreshold
Number of commands sent to subscriber before COMMIT (default 1000)

10. Monitoring Replication Monitor works well, but not perfect
System Stored Procedures
sp_helppublication
= 'publication'
sp_helpdistributor
sp_helpsubscriberinfo
sp_helpsubscription
sp_replcounters
= 'publication'
Perfmon counters
SQLServer: Replication Agents
SQLServer: Replication Dist.
SQLServer: Replication Logreader
SQLServer: Replication Snapshot
Alerts

11. Troubleshooting
Error: “The row was not found at the Subscriber when applying the replicated command”
Use “Continue on data consistency errors.” System Profile for distribution agent
Sets “-SkipErrors” to “2601:2627:20598” OR
Look at error in distribution agent history to obtain transaction sequence number and command ID
Use sp_browsereplcmds to view commands in distribution database
Delete bad command from MSrepl_commands
Error: “Could not find stored procedure 'sp_MSins_blahblahblah“
Replication stored procedure missing at subscriber
Use sp_scriptpublicationcustomprocs to generate stored procedures for publication

12. Troubleshooting
Distribution agents won't start or don't appear to do anything
Possible issue with non-interactive desktop heap
Requires registry change
Microsoft KB article
Snapshot agent cannot complete or distribution agents frequently retry
Possible network issue – check speed and duplex on network cards
All subscriptions show the same latency value
Log Reader Agent may be behind. Use DBCC commands to view transaction log on publisher
DBCC SQLPERF(logspace)
DBCC LOGINFO
Delete commands replicate, even though they were set not to
Management Studio UI bug
Script publication, = N’NONE’

13. Thank you! Questions? kendal.vandyke@gmail.com