Home > Articles > Data > SQL

Maintaining Transactional Replication

  • Print
  • + Share This
Contrary to popular belief, replication is not maintenance-free. As your application and business rules change, so do publications. Baya Pavliashvili dissects the terms and techniques necessary for maintaining transactional replication and gives you sage advice on fine-tuning your replication performance.
Like this article? We recommend

In previous articles of this series, I showed you how to plan for transactional replication, how to set it up, how to monitor it, and how to troubleshoot it. Contrary to what some may think, replication isn't maintenance-free. As your application changes, the set of data and transactions you need to replicate is likely to change, too. For example, when new tables are added to your database and new columns are added to the existing tables, you need to ensure that replication accounts for such changes. Furthermore, at some point after the initial replication setup, you might want to modify publications by adding filters to articles and thereby limiting the number of replicated transactions.

This article discusses the essentials of maintaining previously configured publications. In addition, I'll also tell you about factors affecting replication performance and how to deal with such factors.

Replication Stored Procedures

Before I show you how to modify existing publications, you need to become somewhat familiar with stored procedures executed on subscribers in lieu of commands issued on the publisher.

As discussed in previous articles, transactional replication replaces the INSERT, UPDATE, and DELETE commands that affect published articles with stored procedures. Although this is the default behavior, you can choose to replicate the INSERT, UPDATE, and DELETE commands as they are executed on the publisher. To do so, you can uncheck the check boxes on the Commands tab of the Table Article Properties screen, as shown in the following figure.

Figure 1Figure 1

Keep in mind that the default behavior of executing stored procedures on the subscribers usually provides better performance than simply forwarding commands as they occur on the publishing server.

Stored procedures that are to be executed on subscribers are created during the initial synchronization; when you run the snapshot agent to create a snapshot of published articles, and the distribution agent moves data and indexes to the subscriber(s). Let's take a look at the stored procedures used for transactional replication of the author's table. Here is the procedure replacing the INSERT commands:

CREATE PROCEDURE [sp_MSins_authors] 
@c1 varchar(11),
@c2 varchar(40),
@c3 varchar(20),
@c4 char(12),
@c5 varchar(40),
@c6 varchar(20),
@c7 char(2),
@c8 char(5),
@c9 bit


AS
BEGIN
 
INSERT [authors]( 
[au_id], 
[au_lname], 
[au_fname], 
[phone], 
[address], 
[city], 
[state], 
[zip], 
[contract]
 ) 
values ( @c1, @c2, @c3, @c4, @c5, @c6, @c7, @c8, @c9 )
 
END 

This simple procedure takes nine parameters, one for each column in the authors table. If you happened to add a column to the authors table, you could easily modify sp_msins_authors by adding the new column name and parameter number 10 for the new column.

The DELETE procedure is also very simple—it deletes a row based on the value of the primary key, which is the only parameter this procedure accepts:

CREATE PROCEDURE [sp_MSdel_authors] 
@pkc1 VARCHAR(11) 
AS 
DELETE [authors] 
WHERE [au_id] = @pkc1 

if @@ROWCOUNT= 0 	

if @@microsoftversion>0x07320000 		
exec sp_MSreplraiserror 20598 
GO

Notice that this procedure would raise an error if the value of the @@ROWCOUNT global variable is zero—meaning that no rows were affected on the subscriber when applying the replicated command. Unless you change the primary key column in the article, there is no need to modify the DELETE procedure executed on subscribers.

The stored procedure replacing the UPDATE commands is by far the most complicated. This procedure checks the bitmap parameter to see which columns have changed; it also executes a different subset of code depending on whether the primary key value is being updated. I added some comments and formatted the procedure for readability:

CREATE PROCEDURE [sp_MSupd_authors]  
@c1 VARCHAR(11),
@c2 VARCHAR(40),
@c3 VARCHAR(20),
@c4 CHAR(12),
@c5 VARCHAR(40),
@c6 VARCHAR(20),
@c7 CHAR(2),
@c8 CHAR(5),
@c9 BIT,
@pkc1 VARCHAR(11) ,
@bitmap BINARY(2) 
AS 

IF SUBSTRING(@bitmap,1,1) & 1 = 1 
/* that means primary key value has been modified */
BEGIN 

  UPDATE [authors] SET 
   [au_id] = CASE SUBSTRING(@bitmap,1,1) & 1 WHEN 1 THEN @c1 ELSE [au_id] END ,
   [au_lname] = CASE SUBSTRING(@bitmap,1,1) & 2 WHEN 2 THEN @c2 ELSE [au_lname] END ,
   [au_fname] = CASE SUBSTRING(@bitmap,1,1) & 4 WHEN 4 THEN @c3 ELSE [au_fname] END ,
   [phone] = CASE SUBSTRING(@bitmap,1,1) & 8 WHEN 8 THEN @c4 ELSE [phone] END ,
   [address] = CASE SUBSTRING(@bitmap,1,1) & 16 WHEN 16 THEN @c5 ELSE [address] END ,
   [city] = CASE SUBSTRING(@bitmap,1,1) & 32 WHEN 32 THEN @c6 ELSE [city] END ,
   [state] = CASE SUBSTRING(@bitmap,1,1) & 64 WHEN 64 THEN @c7 ELSE [state] END ,
   [zip] = CASE SUBSTRING(@bitmap,1,1) & 128 WHEN 128 THEN @c8 ELSE [zip] END ,
   [contract] = CASE SUBSTRING(@bitmap,2,1) & 1 WHEN 1 THEN @c9 ELSE [contract] END 
  WHERE [au_id] = @pkc1 

IF @@ROWCOUNT = 0 	
IF @@microsoftversion>0x07320000 		
EXEC sp_MSreplraiserror 20598 
END 

ELSE /* PRIMARY KEY VALUE HASN'T BEEN CHANGED */ 

BEGIN 
  UPDATE [authors] SET 
   [au_lname] = CASE SUBSTRING(@bitmap,1,1) & 2 WHEN 2 THEN @c2 ELSE [au_lname] END ,
   [au_fname] = CASE SUBSTRING(@bitmap,1,1) & 4 WHEN 4 THEN @c3 ELSE [au_fname] END ,
   [phone] = CASE SUBSTRING(@bitmap,1,1) & 8 WHEN 8 THEN @c4 ELSE [phone] END ,
   [address] = CASE SUBSTRING(@bitmap,1,1) & 16 WHEN 16 THEN @c5 ELSE [address] END ,
   [city] = CASE SUBSTRING(@bitmap,1,1) & 32 WHEN 32 THEN @c6 ELSE [city] END ,
   [state] = CASE SUBSTRING(@bitmap,1,1) & 64 WHEN 64 THEN @c7 ELSE [state] END ,
   [zip] = CASE SUBSTRING(@bitmap,1,1) & 128 WHEN 128 THEN @c8 ELSE [zip] END ,
   [contract] = CASE SUBSTRING(@bitmap,2,1) & 1 WHEN 1 THEN @c9 ELSE [contract] END ,
  WHERE [au_id] = @pkc1 

IF @@ROWCOUNT = 0 	
IF @@microsoftversion>0x07320000 		
EXEC sp_msreplraiserror 20598 
END 

As you can tell, the UPDATE procedure uses various portions of the bitmap parameter to see which column has changed. If the column hasn't changed, the procedure sets the column to its existing value. If you add a column to an existing article, the UPDATE procedure will have to change slightly to reflect the new column. We'll see how to do that in a bit.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020