Level: Introductory Timothy Day, IT Specialist, IBM
01 Mar 2005 This article offers some fresh insights about a long-standing question: In which situations is it better to use a server-based Lotus Notes mail file, and when should you use a local replica copy?
IBM Lotus Notes/Domino is widely used email and collaboration software. Lotus Notes allows users to access their email in one of two ways. The first method is to work with a mail database directly from the Domino server. The second method is to create a local replica of the mail database on the user's workstation and to synchronize it periodically. Millions of Notes users are already familiar with these two methods. But what they may not be fully aware of is the answer to this question: When is it best to use server-based mail, and when is it best to work with local mail?
This article seeks to help answer this question. We discuss the relative merits of accessing Lotus Notes email directly from a server versus replicating it to a local file. We also look at the disadvantages of each mail usage method. Our goal is to help you decide which mail method to use in which situations. We assume you have some familiarity with Notes and Domino concepts, although you don't necessarily have to be an expert on Lotus Notes/Domino to understand this article.
Using server-based Notes mail
The most common configuration for accessing Lotus Notes mail is for users to work with mail directly on the Domino server. This is the default configuration that is enabled when a Notes client is configured for a user.
When you use server-based Notes mail, a copy of your mail file resides on a Domino server. Each action that you perform generates a request that is sent to the Domino server and processed, and the results are returned to your Lotus Notes client. These actions produce network traffic and create a slight increase in the workload of the server. Obviously, if no network connection exists, you cannot work with your mail, calendar, or To Dos. Figure 1 shows the basic configuration for server-based mail.
Figure 1. Server-based mail
Advantages of server-based mail
There are several advantages to using server-based mail. The first is that no additional configuration of the Notes client is required. When a Notes client is set up for the first time, it is automatically configured to access mail on the server. All of the bookmarks in Lotus Notes point to databases on the server with the exception of the personal address book and the personal journal.
Another advantage is that data contained in the mail file is always current. All work is performed on the server, so users receive new mail instantly. When a user composes a new message, it is sent instantly to the intended recipient. There is no delay in transmitting or receiving new information.
Mail files that reside only on the server are more easily maintained by administrators. By default, Lotus Domino performs maintenance on mail files nightly, including indexing the database, compacting the database, and pushing out template updates. Users who access their mail files from the server can take advantage of these updates immediately, while users who replicate pull the template changes at the next replication and must perform indexing and compacting of their local mail files manually.
Server-based users also have choices about which client they want to use to access Notes mail. In addition to using the Lotus Notes client, users can access their mail, calendars, or To Dos using Domino Web Access through a Web browser. They can also use a standards-based POP3 or IMAP client to access Notes mail. (Calendars and To Dos cannot be accessed using a POP3 or IMAP client.) Additionally, users can use Domino Access for Microsoft Outlook to access mail, calendars, and To Dos. Depending on how these clients are configured, they can be used interchangeably to access mail and other information.
Disadvantages of server-based mail
There are disadvantages to having users work on the server. Many of these relate to the impact on Notes client performance that occurs when network bottlenecks exist. The first disadvantage is that using server-based mail increases network utilization. This increase is insignificant for a handful of users, but may be noticeable if large numbers of users are accessing the server at the same time. This increase can have a perceptible impact on line speeds where bandwidth is at a premium, such as when users connect to a centrally located Domino server over a low-speed WAN link.
Additionally, if traffic shaping is used to prioritize network traffic for critical applications, such as a database or ERP system, the performance of Notes access may be further impacted. Some of the load on the network can be reduced by using the network compression settings that were introduced in Lotus Notes and Domino 6. Network compression can reduce traffic up to 50 percent in some circumstances and may provide noticeable performance improvements over WAN connections. (See the developerWorks: Lotus article, "Network compression in Domino 6.")
Server-based mail access is not optimal for many remote users. Despite the relative availability of high-speed Internet access, many users still access Lotus Notes mail over a dial-up connection when traveling. Working with mail on the server over a dial-up connection can be a painfully slow experience, especially when coupled with long periods of use or when working with file attachments.
When planned or unplanned server outages occur, users working in a server-based mail environment are unable to access their mail, calendar, or To Dos. Downtime can be eliminated for these users by implementing a Domino cluster. In a clustered environment, users are notified when their home Domino server is unavailable and are then informed when they can access their mail replicas from another server in the cluster.
Sample scenarios for using server-based mail
Your organization should consider deploying server-based Lotus Notes mail in the following situations:
- Administrator or help desk resources are at a premium.
- Users are centrally located and have access to LAN, WAN, or other high-speed access to the server.
- Mail servers are clustered and highly available.
Using local replica-based mail
The second basic configuration for accessing Lotus Notes mail is using a local mail replica of the mail file. In this scenario, you access a replica copy of your mail file from your workstation?s hard drive, rather than from the Domino server. The server is primarily accessed when replicating information to and from the workstation.
One key feature of Lotus Notes and Domino is the ability to maintain the fidelity of data stored in a Domino database across multiple servers or between client and server. This fidelity is achieved through replication between databases stored in different locations. Replication allows data to be synchronized between multiple copies of a database, and it only updates information that changes. Therefore, if you are replicating a mail file with 1,000 messages, and you receive 10 new messages, only those 10 messages are replicated between the client and server. Unlike other protocols, such as POP3 and IMAP, replication allows all data stored in the mail file, including calendar entries and To Dos, to be synchronized between the Notes client and Domino server.
With local replica-based mail, you perform all your mail functions in a replica stored on the hard drive of your workstation. You use replication to create a local instance of a Domino database on your workstation, which allows you to perform many tasks without a network connection to the server. Updates such as receiving new mail or template changes are initially received by the server mail replica. The Notes client then pulls these updates to the local database via replication. Any changes that you have performed on your local mail replica, such as composing new mail, deleting mail, or putting it in a folder, are pushed to the Domino server after receiving new updates via replication. Figure 2 illustrates the basic local replica-based mail setup.
Figure 2. Replica-based mail
Using local replica-based mail allows users to access databases on the workstation without requiring a connection to a Domino server. For example, if you have replicated your mail file to a laptop, you can use your Lotus Notes client to read, create, and edit mail on an airplane, despite the lack of connection back to the Domino server. After you regain network access, you can send the messages that you composed offline and receive any new messages that were received during the interim through replication with the Domino server.
You can implement local replica-based mail in two different flavors. The first of these flavors assumes that users do not have a constant connection to the server. These users usually take the form of business travelers and others who move about frequently because of their jobs. They can perform most of their work offline and connect to the server only to send and receive updates.
The second flavor of local replica-based mail access applies to users who have constant connections to the server, but who work from a local replica. These users have a permanent connection to the Domino server, but perform all of their work locally, only accessing the server for scheduled replication, for new mail, and for address lookups. This scenario is common for users who access Domino via a lower speed WAN or VPN link because it allows them to experience the performance of working locally without the delay in receiving updates that is associated with working offline.
Advantages of local replica-based mail
There are many advantages to setting up Lotus Notes users to access mail from locally based mail replicas. Users who access their mail using a local replica always have access to mail, even when not connected to the Domino server. For example, users who travel can replicate mail before leaving for the airport. While on the plane, they can read and reply to new mail they have received. Upon reaching their destination, they can connect to the network and replicate the changes to the server and pick up any new mail they received during the flight.
For users who do not travel, having a local replica of their mail means that they have access to email even if the Domino server is down. In an unclustered environment, server downtime as a result of a problem or for maintenance results in lost user productivity. Users who access mail using a local replica can still perform work in their mail files during these outage periods.
Users may have a faster experience when performing common tasks when using local replicas of mail. If the network or server is heavily loaded, delays will occur due to the large number of concurrent transactions. Local replica mail users may not notice these delays because the bulk of the processing of mail functions is performed by the Notes client. In addition, server resources are preserved because much of the activity is shifted from the server to the client.
Using local replica-based mail produces less impact on the network. All work is performed on the local workstation, so only updates are sent to and from the server over the network. This is in contrast to network activity being generated for each action done in a server-based mail configuration. According to a March 2004 article published by ePro Magazine:
- Reading and writing mail directly from the server generates 70 percent more network traffic than using local replica-based mail.
- Reading mail directly from the server produces 151 percent more network traffic than when replicating mail and reading it locally.
- Writing mail in a local replica mode results in less network savings than reading it. The difference is because when creating new mail, both the new message written and the saved copy of the message are replicated to the server. In essence, each new message is replicated twice, assuming that a copy of the message is saved in the mail file each time.
Disadvantages of local replica-based mail
There are a number of disadvantages to using local replica-based mail. The primary disadvantage is the complexity of the process. This complexity takes several forms. Additional configuration is required on the Lotus Notes client. By default, local replicas of mail files are not created when configuring a Notes client. As a result, deploying a Notes client with a replica takes longer than when setting it up to access mail only from a server. If an existing user is configured to access locally based mail replicas, the initial replication of the mail file may take a significant amount of time, depending upon the amount of mail and the speed of the network. In addition, administrators need to configure Location documents in the personal address book to optimally support using local mail replicas.
Using local replica-based mail is only supported by the Lotus Notes client. Replication is a Notes and Domino feature and is not supported by other mail clients. Users who work with server-based mail can take advantage of alternative methods to access their mail, such as using Domino Web Access through a Web browser. These alternative methods cannot be used to access a local mail replica.
Users require more training to use local replica-based mail. Most users are familiar with the model of working with mail from the server and do not have an inherent grasp of what it means to replicate. Additional training is required to ensure that users can work with mail in a local replica-based mail configuration, otherwise more support calls will be generated by users who do not understand why they are not receiving new mail. The increase in support calls is more apparent in organizations that deploy server-based mail first, and then later switch to local mail replicas, as opposed to organizations that initially deploy local mail replicas from the start.
When problems arise with a user accessing local mail replicas, additional troubleshooting must be performed by help desk staff. For example, an administrator troubleshooting a problem with a user who is not receiving mail must first verify that mail was received on the server, and then must check that it was replicated successfully. The additional troubleshooting increases the time it takes to close a help desk case.
Because there are now at least two replicas of the mail file, both replicas must be administered. Most of the time, little or no maintenance is performed on local mail replicas because users do not know how to do so. Therefore, tasks such as compact, updall, and fixup are rarely performed on local mail replicas. The lack of preventive maintenance can occasionally result in more incidents of database corruption in local mail replicas. Although data is rarely lost in this situation, the resolution may require a new replica of the mail file to be pulled from the server, which may take a substantial amount of time.
Using local mail replicas requires more workstation resources. Depending on the policies of the organization, users may have very large mail files, and the PC needs the disk storage to handle it. Organizations with workstation hardware that is three or four years old may not have the disk space to accommodate large mail replicas. This concern does not normally exist in organizations with newer workstation hardware.
Users who replicate mail and other corporate data to a workstation run the risk of data being stolen. This problem is a chief concern associated with users who have laptops. When a copy of the data resides on the workstation, if the workstation is compromised, then the data is at risk. The risk of stolen corporate data can be mitigated by encrypting local replicas with varying degrees of encryption. The encryption is tied to the Notes ID file and therefore, is reasonably secure unless the thief knows the password. The weakness in the encryption protection is the user. If the user has an easily guessed password, then encryption may not be foolproof. Also, using encryption is dependant on the user choosing to encrypt the mail and other databases.
When using local replica-based mail, there may be a delay in receiving and sending new mail. This situation is definitely true for users who work primarily offline. This time lag is due to the fact that mail needs to be replicated locally before it is read. This condition can be impacted by the length of time between scheduled replications, or if the Notes client is configured to only perform replication manually. When mail is composed offline, it is not actually sent through the Domino server until the next replication because no network connection exists. As a result, even though the mail may appear to have been sent hours before, the recipient will not receive it until the next time the sender replicates with the server.
The delay is minimized for users who work in a local replica with a connection back to the Domino server. The Notes client will poll the server for new mail, and if it encounters some before the next scheduled replication interval, it will initiate a replication session to pull down the mail before the scheduled replication commences. Although users working in a local replica will still experience some lag while data is transferred from the server, it is offset by the mail polling intervals configurable in the Notes client.
Although users with locally based replicas can still access their mail using other methods, such as Domino Web Access, they may find that the information in the server-based replica is not current. For example, users who work in a local replica may find that their unread marks have not synchronized between the local and server replicas. This problem can be resolved by the option to replicate unread marks introduced in Lotus Notes and Domino 6.0.3 and 6.5.2.
Users may also find that information is not the same between local and server replicas. Two common scenarios where differences may occur are when the user works extensively offline and does not replicate the changes back to the server and if the user configured replication formulas. An example of replication formulas could occur in an organization with a 30-day mail retention policy on the Domino server. A user in this organization may have configured replication so that deletions in the server copy of the mail are not replicated to the local replica. In this case, the local replica of the mail will contain many more messages than the server copy, a condition that may cause confusion for the user and additional help desk calls.
Database links, view links, and doclinks may not work properly when using a local mail replica. For example, suppose you receive a doclink in an email message that has been replicated from the server. If you go offline and click the doclink, an error message is displayed. This error may create the impression that there is a problem with the link. In reality, the error occurs because you are offline and therefore, do not have access to the server. Additional help desk calls may be generated as a result. This situation is only a problem for users who work primarily offline. Users who use a local mail replica and have a persistent connection to the server will usually not encounter this issue.
Finally, when working offline with local mail replicas, the scheduling of conference rooms and resources is not available. You can reserve rooms and resources from the Notes calendar via free time lookups of the server busytime.nsf database (called clubusy.nsf in a Domino cluster environment). Information on a user?s own schedule is accessible when offline, but information of the availability of rooms and resources requires a connection to the server. This limitation also extends to looking up free time information for other employees in the organization, unless the user has added other users to the local Free Time database.
Sample scenarios for using local replica-based mail
The following are examples of when an organization should consider the deployment of local replica-based mail:
- In places where there is no access to a fast and reliable network.
- In places where the network is heavily utilized.
- For traveling users who use dial-up connections.
- For users who require access to information when disconnected from all networks.
Summary
The following table summarizes the advantages and disadvantages of using server-based mail versus local replica-based mail:
|
Type of mail access
|
Advantages
|
Disadvantages
| | Server-based |
- No additional Notes client configuration.
- Information in mail file is always current.
- Easier mail file maintenance.
- Messages and notifications are processed without delay.
- Can use Notes client, Domino Web Access, and other clients to access mail.
|
- Increased network utilization.
- Performance impact by heavy network loads.
- Slower access over dial-up and poor network connections.
- Loss of productivity due to server outages.
| | Local replica-based |
- Access to mail when the server or network is not available.
- Increase in performance when accessing mail.
- Less impact on the network.
|
- Additional configuration of the Notes client.
- Reliance on the Notes client.
- Additional user training.
- Requires additional help desk resources to troubleshoot problems.
- Requires sufficient PC disk space.
- Increased risk of data theft.
- Possible time delay in sending and receiving information.
- Out-of-date information in server-based replica when accessing with another client (for example, Domino Web Access).
- Database links, view links, and doclinks may not work properly when disconnected from the server.
- No lookups of free time when scheduling meetings.
|
As we've shown, there are many advantages and disadvantages to using server-based mail versus local replica-based mail. The good news is that organizations can use a combination of both methods, depending on their user bases. Users centrally located to a Domino server can use server-based mail, while users who connect over low-speed WAN links can use local replica-based mail.
Selecting a method for accessing mail does not preclude a user from switching between access types. For example, a consultant who travels frequently can use local replica-based mail while on the road and use server-based mail when back in the office.
Lotus Notes and Domino provides the flexibility to accommodate the needs of different kinds of users from the traditional office-based worker to the mobile road warrior of the 21st century. Using the information in this article, you can select the method that best fits the needs of your users to enhance the productivity of your organization.
Resources
About the author  | | | Timothy A. Day works for IBM Software Services for Lotus and has seven years of experience with Lotus Notes and Domino. He is currently working with WebSphere Portal and Lotus Companion Products. In his spare time, he enjoys running and has completed two marathons. He resides in Virginia outside of Washington, DC. |
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