Synchronization Fundamentals

In the previous post, we learned how persistent data storage enables users to access enterprise data without being connected to a network. Without enterprise synchronization, the data on the devices would quickly become stale, hence unsuitable for many corporate applications. The synchronization process allows you to execute bidirectional updates on the required data. Any changes that have been made on the client device can be transmitted to the server database, and any changes on the server can be transmitted to the client device. In this way, you can keep the data on the client and the server synchronized.

Whether you are synchronizing over wireless networks or a wireline connection, synchronization offers many important benefits over an always-connected solution, namely:

Reduced data transfer over the network, often leading to reduced transmission costs.

Reduced loads on the enterprise server.

Faster data access, because the user does not have to constantly wait for data to download.

Increased control over data availability.

In the following pages, we will take a look at how synchronization works and introduce features you should consider as part of an enterprise synchronization solution.

TYPES OF SYNCHRONIZATION
The term synchronization applies to more than the movement of enterprise data. It is often used to describe the exchange of personal information management (PIM) data and the transfer of application files. This section briefly explains other types of synchronization before we spend the remainder of this post on the synchronization of enterprise data.

PIM Synchronization
One of the first applications that many corporations make available to mobile workers is email. This is often enabled at the same time as contact lists, to-do lists, and calendar entries. The combination of this data is commonly referred to as PIM data. Wireless access to email is often considered the killer application in the mobile world. It is a subject to which everyone can relate, and the benefits of which most people by now take for granted.

The leading PIM applications on the desktop are Microsoft Outlook and Lotus Notes. Both vendors provide mobile access to PIM data via laptops, so users are familiar with accessing this data remotely. When it comes to smaller mobile devices such as PDAs, a PIM synchronization solution is required to provide this functionality. PIM synchronization solutions allow users to have offline access to their personal information and to synchronize any changes made back into the enterprise system, often without requiring a companion PC.

File/Application Synchronization
Within an organization, a variety of applications and other files need to be distributed to mobile users. In the wired world, this information is often made available through use of portable media such as floppy disks or CD-ROMs or by a corporate server or intranet site. Unfortunately, these techniques do not work nearly as well for mobile workers. Many mobile devices do not have support for traditional portable storage media, and the storage that is available is somewhat expensive, making this an impractical means of distribution. Adding to the challenge is the fact that most users are at remote sites, without access to internal corporate systems.

To overcome these challenges, several file and application synchronization products have come to market. These products allow an administrator to deliver these files to remote workers in an automated way; they require no additional effort by the remote user. This means you can deploy and manage files and applications on remote devices, so you can quickly update remote workers with the applications they need. In most cases, this type of synchronization is one-way: Updates are sent from the server to the remote workers; only an acknowledgment receipt comes back.

Data Synchronization
Data synchronization refers to the bidirectional exchange and transformation of data between two separate data stores. For our purposes, these data stores are most often located on the client device and the enterprise server. In many cases, the synchronized data set is only a subset of the enterprise database. The reason for the limitation is twofold: one, because of the limitations of most mobile devices, and, two, because individual mobile users only require data that is relevant to them.

The data transfer itself occurs between the synchronization layer on the client and the synchronization middleware on the server. The server middleware then communicates with the enterprise data source. This is the most common way that smart client applications are given access to corporate data.