Sonoran Systems

Article KB0010:     20-December-2004

Problem:

How to replicate the ArTrac SQL database in disaster tolerant configurations.

Solution:

NOTE: The following article is reprinted with permission from its author and is provided here as a convenience to you.  Sonoran Systems does not guarantee that all information contained in this article is accurate and assumes no responsibility for its use.  The original article can be found at the following web site:  http://www.mssqlcity.com/Articles/Replic/SetupTR/SetupTR.htm

Setup Transactional replication: step by step guide

Author: Alexander Chigrik
chigrik@mssqlcity.com

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General concepts

Checking necessary conditions

Checking connect

Example

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General concepts

Replication is the process whereby data is copied between databases on the same server or different servers connected by LANs, WANs, or the Internet.

Microsoft SQL Server replication uses a publisher, distributor and subscriber metaphor.

Publisher is the server or database that sends its data to another server or database.

Subscriber is the server or database that receives data from another server or database.

Distributor is the server that manages the flow of data through the replication system. This server contains the distribution database.

Publisher contains publication/publications. Publication is a collection of one or more articles that is sent to a subscriber server or database.

Article is the basic unit of replication and can be a table or a subset of a table.

Subscription is the group of data that a server or database will receive.

There are push and pull subscriptions.

Push subscription is subscription when the publishing server will periodically push transactions out to the subscribing server or database.

Pull subscription is subscription when the subscribing server will periodically connect to the distribution database and pull information.

The Distribution database is a system database, which is stored on the Distributor and does not contain any user tables. This database is used to store snapshot jobs and all transactions waiting to be distributed to Subscribers.

Microsoft SQL Server supports the following replication topologies:

• Central publisher
• Central subscriber
• Central publisher with remote distributor
• Central distributor
• Publishing subscriber

Central publisher

This is one of the most used replication topologies. In this scenario, one server is configured as Publisher and Distributor and another server/servers is/are configured as Subscriber/Subscribers.

Central subscriber

This is a common topology in data warehousing. Many servers or databases replicate their data to a single central server in one or more databases.

Central publisher with remote distributor

In this topology, distribution database resides on another server than publisher. This topology uses for performance reasons when the level of replication activity increases or the server or network resources become constrained. It reduces Publisher loading, but it increases overall network traffic.

This topology requires separate Microsoft SQL Server installations, one for the Publisher and one for the Distributor.

Central distributor

In this topology, several publishers use only one distributor, which resides on another server than publishers. This is one of the most unused replication topologies, because it has only single point of failure (on the single server with central distributor), and if distributor's server will fail, entire replication scenario will be destroyed.

Publishing subscriber

This is a dual role topology. In this topology, two servers publish the same data. One publishing server sends data to subscriber, and then this subscriber publish data to any number of other subscribers. This is useful when a Publisher should send data to Subscribers over a slow or expensive communications link.

Checking necessary conditions

Check the following before setting up transactional replication:

1. Remember that Microsoft SQL Desktop Edition supports only subscriptions to transaction replication. So, you must use Microsoft SQL Standard, Enterprise or Small Business Server (SBS) editions to publish transaction replication. So, for publish transaction replication you should have Windows NT Server, Windows NT Server Enterprise Edition or Windows NT Small Business Server (on Windows NT WorkStation and Windows 9x you can install only SQL Server Desktop Edition).

2. The Localsystem account has no access to shares on the network as it isn't an authenticated network account. So, if you want to setting up replication you should change the account the MSSQLServer and SQLServerAgent services runs under to an account with the Windows NT administrator's rights.

3. Only members of the sysadmin fixed server role can set up and configure replication, so if you have not these rights, you can not set up replication.

4. You must uncheck trunc. log on chkpt option, if you want to set up transactional replication.

5. Allocate adequate log space for each database that will be published in transactional replication.

6. Allocate adequate disk space for the distribution database.

7. Ensure the server that is being replicated to, is defined as a remote server.

Checking connect

1. Check TCP/IP by using ping utility.

2. Check odbc connection by using odbcping utility.

This is the syntax of odbcping utility:

odbcping [-S Server | -D DSN] [-U Login Id] [-P Password]

If you have received the message like below, the SQL Server works okay:

CONNECTED TO SQL SERVER ODBC SQL Server Driver Version: 03.70.0623 SQL Server Version: Microsoft SQL Server 7.00 - 7.00.623 (Intel X86) Nov 23 1998 21:08:09 Copyright (c) 1988-1998 Microsoft Corporation Standard Edition on Windows NT 4.0 (Build 1381: Service Pack 4)

Example

In this example, I will use two servers: CHIGRIK_A_U - publisher and distributor and MAKSIMUK_I_L - subscriber. I will use transactional replication with push subscription.

Register new remote server in which will be replicated.

Enter the name of remote server and specify Remote Login Mapping:

If you have made all correctly, you receive the following:

Select Tools -> Replication -> Configure Publishing and Subscribers:

This will launch the Configure Publishing and Distribution Wizard:

Select the Next button to create the Distributor:

Now, you can choose the default settings or set the distribution database name and location, enable other Publishers, or set another settings. Click the Next button.

Click the Finish button.

Now, SQL Server creates the distribution database, enables publishing, and setting up the distributor:

Because we installed CHIGRIK_A_U as Distributor, the Replication monitor has been added to the console tree on the CHIGRIK_A_U server.

Now, we are ready to start creating publications and articles. Select Tools -> Replication -> Create and Manage Publications:

You will see Create and Manage Publications dialog box:

Choose pubs database and click the Create Publication button.

This will launch the Create Publication wizard.

Select Transactional publication and click Next button.

You can allow immediate-updating subscriptions on this step. If you choose this option then all changes will be applied at the Subscriber and Publisher simultaneously.

Choose Subscriber types on this step. If all subscribers are Microsoft SQL Server subscribers, choose the first option.

Select tables or stored procedures to publish and click Next button.

Choose publication name and description on this step.

You can define data filters or set another options on this step.

Click Finish button to create the publication.

If publication was created successfully, you will receive the above message.

Create new push subscription now.

Click Next button.

Choose subscribers. Click Next button.

Choose destination database. It's pubs database on the MAKSIMUK_I_L server.

If you want to have continuous replication that will send the data as soon as possible, you can choose Continuously option. Otherwise, choose schedule option. Select the Continuously option and click the Next button.

Initialize subscription if it's needed.

Click Next button.

Click Finish button to create the subscription. Now, you will receive the following: