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SQL Server 2012 Upgrade Technical Guide
For a side-by-side upgrade, first restore the SQL Server 2000 databases to SQL
Server 2005, 2008, or 2008 R2 and then restore the resulting database to SQL
Server 2012.
Comparing In-Place and Side-by-Side Methods
Table 1 summarizes the difference between the two upgrade strategies. Be aware that
the main difference between an in-place upgrade and a side-by-side upgrade depends
on the resulting instances. An in-place upgrade replaces the old instance so that only
one instance remains.
Table 1: Characteristics of an In-Place Upgrade vs. a Side-by-Side Upgrade
Process
In-Place Upgrade
Side-by-Side Upgrade
Number of resulting instances
One only
Two
Number of physical servers involved
One
One or more
Data file transfer
Automatic
Manual
SQL Server instance configuration
Automatic
Manual
Supporting tool
SQL Server Setup
Several data transfer methods
Another way to view the differences between an in-place upgrade and a side-by-side
upgrade is to focus on how much of the legacy instance you want to upgrade. Table 2
shows how you can use the component level of the upgrade, combined with the
resulting number of instances, to determine what upgrade strategies are available for
your needs.
Table 2: Upgrade Strategies and Components
Component Level
Single Resulting Instance
of SQL Server 2012
Two Resulting Instances
All components
In-place
Side-by-side
Single component
In-place
Side-by-side
Single database
Not available
Side-by-side
The overall advantages of an in-place upgrade include the following:
An in-place upgrade can be easier and faster, especially for small systems,
because data and configuration options do not have to be manually transferred
to a new server.
It is mostly an automated process.
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SQL Server 2012 Upgrade Technical Guide
The resulting upgraded instance has the same name as the original.
Applications continue to connect to the same instance name.
No additional hardware is required because only the one instance is involved.
However additional disk is required by Setup (see "Setup Requirements for an
In-Place Upgrade" in the "SQL Server 2012 Setup" section later in this chapter).
Because it is mostly automated, it takes the least deployment team resources.
Some overall disadvantages of an in-place upgrade include the following:
You must upgrade the whole instance or a major SQL Server component. For
example, you cannot directly upgrade a single database.
You must inspect the whole instance for backward-compatibility issues and
address any blocking issues before SQL Server 2012 Setup can continue.
Upgrading in place is not recommended for all SQL Server components, such as
some DTS packages. See Chapter 17, "Integration Services," for more
information about how to upgrade DTS packages.
Because the new instance of SQL Server 2012 replaces the legacy instance, you
cannot run the two instances side by side to compare them. Instead, you should
use a test environment for comparisons.
Rollback of upgraded data and the upgraded instance in an in-place upgrade
can be complex and time-consuming. See "Rolling Back an Upgrade" later in this
section for more information.
The overall advantages of a side-by-side upgrade include the following:
It gives more granular control over which database objects are upgraded.
The legacy database server can run alongside the new server. You can perform
test upgrades and research and resolve compatibility issues without disturbing
the production system.
The legacy database server remains available during the upgrade, although it
cannot be updated for at least the time that is required to transfer data.
Users can be moved from the legacy system in a staged manner instead of all at
the same time. Even though your system might have passed all validation and
acceptance tests, a problem could still occur. But if a problem does occur, you
will be able to roll back to the legacy system.
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SQL Server 2012 Upgrade Technical Guide
The overall disadvantages of a side-by-side upgrade include the following:
A side-by-side upgrade might require new or additional hardware resources.
If the side-by-side upgrade occurs on the same server, there might be
insufficient resources to run both instances alongside one another.
Applications and users must be redirected to a new instance. This redirection
might require some recoding in the application.
You must manually transfer data—as well as security, configuration settings, and
other supporting objects—to the new instance.
Synchronization of data from the legacy server to a new server will be required
to capture data modifications that occurred to the legacy system while setting
up the new system and its original copy of the data.
Summary of Factors Affecting the Upgrade Strategy Decision
Sometimes it is expediency, disk space, new server hardware, or high availability
considerations that will help you decide which upgrade strategy to use. Use your best
judgment to decide which, because there are no simple rules to follow. Table 3 is
intended to give you some guidelines for your consideration as you make your
decisions. And be aware that you might decide to upgrade some of your instances in-
place and other instances side-by-side, depending on your organization’s needs. Many
of these factors are discussed in more detail later in this chapter.
Table 3: Summary of Factors Affecting the Upgrade Strategy Decision
Consideration
In-Place Upgrade
Advantages
Side-by-Side Upgrade Advantages
Require the fewest
hours for the upgrade
deployment team to
plan and prepare the
upgrade effort
Setup automatically upgrades
data and settings in place,
without the need for a manual
transfer of data or settings.
The resulting upgraded
instance has the same name as
the original.
Applications continue to
connect to the same instance
name.
It gives more granular control over which
database objects are migrated.
The legacy database server can run
alongside the new server. You can perform
test migrations and research and resolve
compatibility issues without disturbing the
production system.
The legacy database server remains available
during the migration, although it cannot be
updated for at least the time that is required
to transfer data.
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