If the Registry is severely damaged, access to hardware and software may be drastically limited, and the system may not even boot. Even in a case of a minor problem, an application may not work as it was designed, or may perform erratically.
Although Registry problems are rare, when they occur it can be devastating to the system, to applications, or even to data. The Registry is protected while it is running, so it is not possible to copy, delete, or change the contents, except through a "certified" program (installation programs, registry editing tools, and security changes through User Manager for Domains and the Explorer). Because of this protection, the Registry is quite secure--but it is not bulletproof. Problems can and do occur, and you need to be prepared to recognize them so you can fix them.
Most of us have heard of or felt the following symptoms, all of them characteristic of Registry problems:
Figure 3.1. An example of the Blue Screen of Death in Windows NT.
NOTE: The STOP message in Windows NT (lovingly called the Blue Screen of Death) identifies the type of exception. The second line qualifies the exception, showing whether it was user mode (involving user-mode operating system software) or kernel mode (involving the operating system or third-party drivers or hardware). The third and fourth lines describe which components were actually involved and at what addresses. The error in Figure 3.1 shows that it was a SCSI driver that failed. Check for compatibility and be sure you have the correct driver. It could also be that the settings were in error, meaning either they were wrong when they were added, or the Registry got corrupted and reported them incorrectly.
Each one of the symptoms or complaints listed is serious, although the seriousness of the problems varies. In any case, Registry problems will force you to take the time for repair, wasting precious productivity for your organization.
Recognizing the actual problem may not be as easy as recognizing the symptom. When problems occur, you generally assume, rightly or not, that it was something you did. That seems to be ingrained in us from our youth. For example, if a program starts acting strangely, we try to retrace our keystrokes to determine our mistakes. This is reinforced by the first question that comes from the mouths of support staff: "What did you do?" (with emphasis placed on different words based on their disposition at the time).
It might not even have anything to do with user mistakes. Problems in the Registry occur for various reasons, and often the symptoms mask the real nature of the problem.
Rather than dealing with the symptoms, deal with the problems that can occur. With every type of control available through the Registry, there is a corresponding potential problem, as illustrated in Figure 3.2.
Sometimes, it feels like a whole set of dominoes
falling down. One problem affects
another, which limits the use of another item, and so on. An example would be the
effect of a Registry error in the configuration of a network card. Without the correct
information, the card cannot be activated.
Without the card activated, no data can
be transferred on the network, the server cannot be contacted for logon, and no user
validation is possible. The user gets an error message that no domain controller
can be found, and network resources may not
be available. Is it really a problem
with the server? Not at all.
Figure 3.2. The
cascading effects of errors in the Registry.
The process can be difficult to stop, and often it is difficult to determine exactly what caused it and where it started.
It is obvious, however, where it ends: a loss of productivity for the organization, wasted time, and possibly even severe financial losses.
If the Registry gets corrupted for any reason, system or application functions may fail, and a support technician must isolate the problem and repair it.
The Registry normally works, most of the time, without any problems. It can, however, get corrupted in many ways. Programs that you add to the system, system changes and problems, and manual changes are the three main ways that errors are introduced. Of course, the results of these errors can vary in their scope and seriousness.
The three most common ways the Registry gets corrupted are
It is impossible to prevent all errors from happening. If you know what can happen, it is easier to troubleshoot errors. By protecting the Registry (as outlined in Chapter 4, "Protecting the NT Registry," and Chapter 6, "Protecting the Windows 95 Registry"), you always have a safety net. By using the tools and procedures discussed in Chapter 5, "Recovering from an NT Registry Failure," and in Chapter 7, "Recovering from a Windows 95 Registry Failure," you can recover from even the most severe problems. Take a look at each of the types of problems in more depth.
Adding and removing programs account for the majority of errors found in the Registry. Most users add between six and seven applications, and add or upgrade drivers, four or five times per year. During initial installation and setup, the numbers are even greater.
WARNING: One of the original requirements for programs to receive the "Designed for Windows 95" logo was that the application is also compatible with Windows NT. That requirement has been reduced to "tested on Windows NT." At the very worst, if the application doesn't work with NT, it is supposed to "degrade gracefully," which means it will not damage NT. Unfortunately, that is not always the case, particularly with applications that use Plug and Play. With no support from NT for Plug and Play, many applications make unfortunate assumptions that create serious problems in the Registry. To their credit, Microsoft shipped a Software Compatibility List with the early betas of NT 4.0. Unfortunately, they did not continue that with the shipping version, assuming that all the applications in the Windows 95 list would work. Here are the most common reasons that applications cause problems with the Registry:
NOTE: It sounds as if I don't appreciate programmers. Actually, I do. I believe they do a tremendous job, even when faced with unbelievable deadlines, massive budget cuts, incredible hours, and more tedium than most people could ever live through. I am amazed daily that computers and software can do what is considered commonplace. Keep it up.
NOTE: Because of the relationship between Windows 95 and Plug and Play, drivers in Windows 95 normally do not have the same problem as in Windows NT. If a driver is replaced on the hard disk by accident, or if the firmware changes, Windows 95 will simply install a new driver.
Figure 3.3. The actual font does not match the name of the font.
Unfortunately, you may find out about these problems too late, after you have lost
time, money, and/or data. Also, you are almost powerless to truly solve them, because
someone else wrote the
program, and most people do not have the expertise required
to change the application itself. The best you can do as an administrator is to repair
the Registry and look for an update or replacement.
If the computer system itself has a problem, the Registry can become corrupted. Usually, these errors can be prevented with proper system care and management.
TIP: Windows NT is actually quite resistant to most strains of computer viruses. For example, it will not allow viruses to invade the boot sector. Some of the new viruses, such as Word macro viruses, can be devastating to the Registry. A simple virus-checking program, such as those from Symantec/Norton Utilities and McAfee and Associates, works very well.
Figure 3.4. Changing the Maximum Registry Size.
WARNING: Reducing the size of the paging file in the Virtual Memory portion of the System section of the Control Panel in NT may reduce the maximum Registry size. Even though the system will warn you, some of those warnings go unheeded, and the Registry may be in peril. It is highly recommended that you make sure the maximum Registry size is at least 2MB larger than the current size. If you are going to be adding hardware or several new user accounts, check this before proceeding.
This is not a problem in Windows 95; it always has a variable size for the Registry.
TIP: Windows NT file systems include the capability to hot-fix the drive (that is, repair errors on the fly) most of the time without your even being aware that there was a problem. If you have a Registry problem resulting in the Blue Screen of Death, it may help to run CHKDSK.EXE from the \WINNT\SYSTEM32 directory.
When people manually edit the Registry, they are prone to make errors because of the complexity of the data, and the errors may be significant enough to cause the system to quit working. It is very unfortunate that Microsoft has chosen to deal with the Registry and Registry editing as a "black art," leaving many people in the dark as to the real uses of all the settings in the systems.
Microsoft's refusal to adequately, and publicly, supply information about the correct settings is extremely frustrating to system administrators. Certainly, more damage has and will be done because of lack of knowledge than because of too much information. Most of the actual edited changes that are made by users are done with the Registry editors.
Copying other Registries is a very serious mistake many users make. Just because it works on the other machine doesn't mean it will automatically work on this one. Much of what is in the Registry is specific to the individual system, even if the hardware is the same. Copying the files that make up the Registry to another system will not work. Characteristically, if another system's Registry is used, most of the hardware will not work, and user and security issues may make the data and application information inaccessible.
There are some parts of the Registry items that can be used for another system, however, and the special procedure for doing that is shown in Chapter 11, "Remote Registry Editing."
If you could eliminate all the problems listed in this chapter, Windows NT and 95 would run without failure almost indefinitely. That is probably not realistic. However, knowing how the Registry can get corrupted can help you use better system-management techniques and may prompt you to take better care of it.
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