There is one consideration that you should carefully think about if you are going to use ISA—namely, the issue of security. You should be very careful if the Web address of the server is outside of your own firewall or is visible to the outside world on the Internet. Your Internet server will be running as user "Informix" and anyone who can log on to the server as user Informix with the proper password will have DBA privileges on your server. As you will see, ISA gives you powerful command-line and SQL scripting abilities, and these could be very dangerous to your system if they were to be compromised by a hacker.

You may think that just using a non-standard port number instead of the traditional port 80 for HTTP on most systems would serve as some defense against an attack, but the fact is that most hackers have access to sniffers and other methods that can probe the active ports on a remote system. At the very least, use a very strong password for the Informix user.

Notice that each Informix server to be monitored must have its own Web server as well as its own database server. Hopefully, either users or Informix will work out a method to get around this limitation, as it is not a trivial task to install, configure, and maintain separate Web servers for each database server. Until that happens, when you want to work with a database on another machine, you will have to enter the URL of the machine. If nothing else, it should be simple to create an HTML page that lists the servers to monitor and allows you to link to them without having to enter individual URLs.

When you first log on to an ISA URL, you will be prompted for a username and a password. You need to enter the Informix username and its associated password. You will also get a first page summary screen in which you need to click on "Use ISA" to get to the first real page of the system.

In Figure 1 you can see a series of links across the top. The first one, "Manage another server," brings you back to this page to select another server on the same computer. The "Answers Online" and "Developer Network" links take you to pages on the Informix Web site, so unless you are connected to the Internet, these links will not work.

Figure 1: The ISA main page

One of the best features of ISA is its Help function. When you click on the "View Help" link, you get help from the target server rather than from an Internet site. Help will then always be available whether or not you are connected to the Internet.

Notice in Figure 2 that there is now a list of links along the left-hand side of the page. Clicking on any of these links will bring up a help page on the subject. Most of these pages also explain the source and meaning of the data.

Figure 2: The ISA help system

Because ISA functions by performing regular Informix utilities such as "onstat" and parsing the results for the Web, paying attention to the commands underlying the page will help you become more familiar with the command-line utilities as well. Use the help system. It's a great resource.

Referring back to Figure 1, in the middle of the screen you can see a listing of Informix servers on the target. You will only see multiple servers on this page if you have multiple instances running on the same system. Note that ISA also supports Informix's clustered products. I have not tested how they will appear in ISA. To choose a server to monitor, click on the server name. In Figure 1, I clicked on ol_scsibox, which is the name of the sole Informix instance running on the NT server: scsibox.

There are some new elements Figure 3, which are fairly consistent throughout ISA. First, the blue section at the top now includes header information about the instance you are monitoring. This gives the same information as the headers from the onstat commands: instance name, uptime, operational status (quiescent, online, offline), memory usage, and Informix version number. Below that, ISA gives a brief summary that includes the number of sessions and read/write cache hit rates. Below this section is a table showing recent entries in the Informix message log.

Figure 3: Main server monitoring page

Also, to the left you can see a vertical bar with links to various other functions within ISA. This bar is actually a hierarchical outline view of multiple pages within the ISA Web site. This menu changes depending upon where you are in ISA.

Figure 4 shows a view of what you see when you scroll all the way down Figure 3. There are several elements of interest here.

Figure 4: Bottom of main server monitoring page

First, notice the Refresh button along with a text box asking for a refresh interval value. This allows you to set up the page to automatically refresh every x seconds. This may not be very meaningful when looking at log outputs, but other pages that give important performance data can sometimes be more easily understood by looking at the way the data changes over time. I'll give an example of this later, but first let's look at the links across the bottom of the page, specifically the Command button. When you click this button, you get Figure 5.

Figure 5: Command mode

OK, this looks fairly innocuous—that is, if you consider giving some nameless hacker full command of your Informix database from out on the Web somewhere. Let's look at what might get entered here.

Figure 6: The DBA hacker from hell

Do you want to bet that I very carefully typed in the command line and very carefully did not touch the Execute button when I took the screen shot for Figure 6? This gives you an idea of why it is so important to get your security down very well before exposing this to a wide audience.

We're not going to go over all of the functions of ISA. Part of the fun of using the tool is the pleasure of discovering just what it will do. One of the big advantages of the concept of using a browser as a user interface is that the training time is nil; you already know how to surf the Web via a browser. Now you just surf the ISA application with the same browser.

I now hit on the high points of the ISA monitoring window so that you'll be prepared with a few things to watch for, as well as to watch out for.

The main menu has the following items:

• Check runs various flavors of uncheck that can check the disk structures used by Informix and can fix some of the errors that it finds. This can potentially interfere with normal database operations, and it is best to run this at an off time.
  
• Configuration allows you to change various parameters on the server. Of particular interest in the ONCONFIG link, which will show you the ONCONFIG file for the given instance. The neat part is the little button at the very bottom, which allows you to edit the ONCONFIG file. You can see and edit many important files in this manner, and it greatly simplifies administration of a remote server.
  
• Logs gives you various statistics on your physical and logical log usage. Be careful with the ONLOG link, as it is possible to freeze up a database while you are viewing the current log. Unless you are the only user of the database, it's a great way to make enemies amongst the users.
  
• Memory gives you massive amounts of information about the memory use of the server. It also allows you to add memory segments and to free unused ones. This section is best used by the advanced tuner.
  
• Message Log shows you a portion of the message log. You've already seen part of this in the Summary section, which is the entry page into the server.
  
• Mode allows you to start and stop the server and to move into quiescent or online mode. This is another example of why security is so important. Do you really want Web surfers doing this?
  
• Performance probably the most useful of all the statistics for the DBA. It includes extensive information about I/O, buffer usage, resource usage, memory usage, network usage, and disk space. Combined with the capability to auto-refresh, the DBA can monitor just about all of the internal workings of the Informix engine.
  
• SQL allows the user to execute SQL statements from the Web browser. This attempts to be a replacement for dbaccess and sqleditor, but it only succeeds marginally. This is simply data retrieval into a Web page. There are none of the slick features of sqleditor, such as saved queries, multiple result sets, multiple SQL statements, or partial execution. Informix needs a lot of work on this functionality to make ISA a much more useful tool.
  
• Storage allows the user to inspect and modify the disk storage structures in Informix. You can add or delete chunks or dbspaces as well as modify the mirroring status of the engine.
  
• Summary is the first page the user sees after choosing a server to monitor. You've already seen this.
  
• Users shows data about users connected to the system: their sessions, threads, and transactions.
  
• VPs shows data about the virtual processors (VPs) in the system and allows you to add new VPs.
  
• XPS is an entire section for the extended parallel server (XPS). Who knows what the product-name-du-jour is this week? They seem to rename the product on a weekly basis.
  
• Index by Utility is a very useful feature, a cross-reference and help screen for most of the major online utilities such as onstat, onlog, and onspaces. In addition to giving a fairly complete list of options and usage, it also links the user to the Web page in ISA that uses that option.
  
• Command allows you to run operating system commands as user Informix on the target machine. You've already seen this.
  
• Custom goes into a tutorial that shows you how to extend ISA with your own pages and commands.
  
• Enterprise Replication allows you to manage replication across servers.
  
• Onbar allows you to monitor and control the onbar backup system.