Replication is something unique to Lotus Notes. This appendix explains
What replication is
How replication works
How to replicate your databases to and from the server
Domino data is stored in databases that are usually hosted by Domino servers, but which may also be hosted by your own Notes client. A given database might be hosted by a single Domino server or Notes workstation or by multiple machines—one or more Domino servers and possibly multiple users’ Notes workstations as well.
The primary reason why a database may exist on multiple machines is so that users can gain access to the data more quickly and conveniently. Notes can deliver locally stored data to you more quickly than data stored on a Domino server. It can deliver data stored on a nearby server more quickly than data on a server half-way round the world.
But there’s a problem with permitting databases to reside on multiple computers, which is that the content of the databases changes from time to time and somehow the changes have to get copied to the other copies of each database. The process of copying such changes is called replication. It is actually a special copying process. Replication does not overwrite the entire database, as copying a database would in your file system. Instead, it updates only the documents that have been modified (and, in fact, only the changed fields within those documents).
Note
Although many programs use replication to move copies of data closer to the users, Notes is unusual in that, by default, it allows users to make changes to the data in any copy of the database. If you and I both change the same piece of data on two different copies of a database, we create a replication conflict. The servers will do their best to resolve the conflict, but may not be able to do so, in which case a human being will have to do so. Most other distributed database applications avoid this problem by requiring all changes to occur on a single master copy of the database, all others being read-only copies.
As a user, you need to know two things about replication. First, a given database might reside on multiple servers; you want to access the database on the closest one. Generally, your administrator can configure Domino so that, when you go looking for a database the first time, you will only find the one closest to you. But if you travel a lot, you might occasionally want to connect to a different copy of the database than the normal one.
Second, you may need to know how to create and maintain replicas on your own Notes workstation. If you travel a lot or work from home and have to use a modem to connect to other computers, you will really appreciate Notes’s ability to store local replicas of your server-resident databases. Not only will it be painfully slow to retrieve in real time each bit of data over the slow telephone connection, but the telephone connection might be costly. On the other hand, even if you only ever use Notes in your office at work, you might still find yourself using a local copy of your mail database if the network administrators need to conserve network resources. If so, you need to know how to initiate replication with your server.
Note
Home Server is the term used for the Domino server on which your mail database resides. If you can access several Domino servers at work, the one containing your mail database is your home server.
When you are ready to replicate a database, you’ll connect to the server in your office. After the two computers “shake hands” and recognize each other, your computer begins sending updates you made to your database replicas. Then your computer receives any modifications made to the server’s replicas since you last replicated.
Now look at replication with regard to your Mail database. To receive your mail, you connect to the server from home (or from the road) and replicate your Mail database. After you disconnect from the server, you read your mail, reply to some messages, delete some messages, and file some messages in folders. During this time, Mary Jones sends a new mail message to you, which is waiting on the server replica of your mail database. When you finish reading and replying to mail, you reconnect to the server and replicate mail again. During this replication period, the changes you made while disconnected (new replies, deletions, and so forth) are sent to the server copy of your mail database, and Mary’s new message is sent to your replica of the database.
Each database has a unique replica ID that identifies it as a genuine replica and not just a copy of the database (you can see it on the Info tab of the Database properties box). If the database on your computer does not have the same ID as the one on the server, replication won’t occur.
Before replicating, the server also checks to see when the replica copy of the database on your computer was last modified. If that date is more recent than the date the database was last successfully replicated, the database replicates. The server also looks at the modification and replication dates on the server replica. If that replica was modified since the last replication, replication occurs. Domino maintains a replication history of each database you replicate (choose File, Replication, History to view the replication history of the database you have open).
When the database replicates, it updates only those document fields that have been changed since the last replication, and adds any new documents. Each document has its own unique Notes identification number (UNID) assigned to it when it is first saved (you can see it on the Document IDs tab of the Document properties box). Part of that number is a document-level sequence number that increases each time you modify the document. If the number is higher for a particular document than in the database on the server, it is replicated to the server. Any documents that you deleted or that were deleted from the server replica leave a deletion stub, and that is replicated so the document is deleted from other replicas of the database, unless Do not send deletions was checked in the replication settings dialog box.
When replication is complete, you disconnect. You now have an updated copy of the database on your PC.
You can control the replication process by specifying what type of files you want to receive, how old the files can be, and the priority of the database replication. All this is controlled under Replication Settings. There are three ways to open the Replication Settings dialog box for the database you have open or selected:
The Replication Settings dialog box has five pages of settings—Basics, Space Savers, Send, Other, and Advanced. You click the appropriate tab to change pages.
On the Basics page, you enable a replication schedule, decide how much of the database you want replicated, and select a preferred server for replication. The purpose of the options on the Space Savers page is to limit the amount of space the replica takes up on your hard disk. The Send page includes options about what types of items you want to send when replicating with the server. On the Other page, you can disable replication temporarily, specify the priority of the replication, and enter the CD-ROM publishing date. The Advanced page has options to control server-to-server replication, which is beyond the scope of our discussion. Table B.1 quickly summarizes the important features of the dialog box that you might need to use.
Note
Check with your Domino administrator before you begin changing replication settings or try to create a mail replica. The administrator may have set that up for you when your Notes client was installed. If not, the administrator may want to walk you through the steps or do it for you.
Note
If you work with local replica databases, be sure to take advantage of streaming replication. In Replication Settings, under Basics, in the Receive documents from server field, choose Smallest First. This will enable you to start reading your earliest incoming documents while the later, larger ones are still being replicated to your computer.
Table B.1. Important Replication Settings Options
People who use their computers outside the office and away from the network are referred to as mobile users. If you’re a mobile user, it’s a good idea to replicate the important databases you need to your laptop before you take the laptop out of the office. This will save you time on the telephone lines (if you use a modem). Of course, the most important of the databases you want to replicate is your mail database. Before you begin, confirm with your Domino administrator that you need to make a new Mail database replica. There could be a copy on your laptop that doesn’t have a bookmark associated with it. To find out if a replica is on your computer, right-click the bookmark for your mail file and choose Open Replica. If local appears in the list of replicas, you already have the replica on your laptop. Notes is smart enough to place local replica information on the bookmark when you have opened the server copy, if the local replica exists.
Making a new replica is a straightforward process. Later in this appendix, the section “Using the Replication Page” shows you how to update this replica (or replicate) on an ongoing basis.
Open your mail database, and then choose File, Replication, New Replica from the menu (or right-click the bookmark, and choose Replication, New Replica from the menu).
The Create Replica for Database [database title] dialog box appears (see Figure B.1).
Make sure the Server displayed is Local. Notes automatically fills in the Database and the File path. You can change the path to put the file in a different location if you want, but if you are making a replication of your mail database, you should not change the target location. If you do, your mail bookmarks won’t work correctly.
Click the twistie by Replica Settings, and then select Create Immediately.
Click OK.
After this, any time you want to replicate (update) your mail, use the Replication page, as shown in Figure B.2.
The Replication page provides a central location to handle all your replication needs. By using the features available on the Replication page (see Figure B.2), you can set options to control which databases replicate and with which servers you are replicating. To open the Replication page, click the Replication bookmark on the Bookmark bar.
Figure B.2. While you are replicating, you can see the progress of the replication at the bottom of the Replication page.
There are several rows, or entries, on the Replication page:
Send outgoing mail and Send outgoing Internet mail—. Sends all pending messages from your Outgoing Mail databases. These databases hold your outgoing mail when you work offline. When you use the Replication page, the outgoing mail gets routed to the server.
Databases—. For each local database replica that you have, such as Mail, there is a database entry on the Replicator page.
Database templates—. Templates are used to create new databases and to refresh the designs of any template-based databases you have. You probably will not need to replicate your templates with the server. (You need to do this only to update your templates.)
Local free time info—. Your mail server keeps track of its mail users’ calendar entries so that, when we want to schedule a meeting, we can see when potential attendees are free. When working offline, we don’t have access to that information on the server. By right-clicking this entry and setting appropriate options, we can store other people’s busy times locally, so as to gain this same benefit while working offline.
Call server and Hang up—. These entries automatically appear when you choose any location configured for connecting to servers via a modem. When you activate replication, these entries place the phone call and then hang up automatically when replication is completed.
Each entry row also has a check box. To include an entry in the replication, click the check box (a check mark appears). When you click the Start Now button (select Start Mail Only Now from the drop-down menu to replicate the mail files only), Lotus Notes performs the functions of each checked entry row in the order of the rows.
The Status bar at the bottom of the page shows information about the current replication, letting you know when Lotus Notes is attempting to call a server, what database is being replicated, the progress of the replication, how many minutes are left, and when the replication is finished. After replication, the status bar displays statistics for individual entries.
If you regularly work with local copies of databases, you may want to set up scheduled replication, so that you don’t have to remember to initiate replication all the time. This would be beneficial to you if you regularly work from home or if your administrator requires you to work from a local replica of your mail database.
You can set up scheduled replication in two places—your location document (under the Replication tab) or the Replication page. All you have to do is choose to enable it. Notes will thereafter attempt to replicate with each appropriate server every 60 minutes as long as Notes is running. You can further refine this, again in the location document or the Replication page. In the Replication page, you can choose Set Replication Schedule on the Replication page to open a dialog box of replication settings. In the location document the same replication settings appear directly when you enable replication.
The available replication settings are described below:
Create new replicas—. The options are Immediately and Next Replication. This sets the default behavior for whenever you create a new local replica. If you choose Immediately, the new replica will be created then fully populated with documents from the server while you wait. If you choose Next Replication, the new replica will be created immediately, but it won’t be populated with new documents until the next time replication occurs with the server from which the replica was created.
Replicate when Notes starts—. If you select this, you can choose two further options: Prompt before replicating and Don’t prompt. Either Notes will replicate with appropriate servers when it first starts or it will prompt you to tell it whether or not to do so.
Schedule—. Selecting this reveals the next three listed options, allowing you to refine the replication schedule.
Replicate daily between—. The default is 8:00 AM–10:00 PM, meaning that scheduled replication will take place between those hours. You can change the time range. You can also set multiple time ranges, or you can set individual times. Separate individual times or ranges with semicolons.
Repeat every—. The default is 60 minutes, meaning that replication will repeat every 60 minutes. You can change this time interval. If you chose individual times in the previous field, this number has no effect.
Days of week—. You can choose on which days of the week scheduled replication will take place. The default (all or none selected) is every day of the week.
Replicate when Notes ends—. Select this if you want Notes to replicate when you shut it down. If you do select this, two other options will appear, permitting you to tell Notes to replicate on shutdown only under the following circumstances: If anything is waiting to be sent and If outbox is not empty.
High priority replication—. Selecting this checkbox reveals a second set of scheduling fields (Replicate daily between, Repeat every, and Days of week), permitting you to define a different replication schedule for high priority databases. You can set a database as high priority in the Replication Settings dialog box. The benefit here is that you could have high priority databases replicate frequently, others less frequently. You could, for example, retrieve new mail every 15 minutes but other data every few hours.