Logging Guidelines

Because logging functions are general purpose, developers must decide what information is appropriate to log. It is important to note that logging consumes resources: disk space and logging time. The event log is not intended to be used as a trace facility.

You should log information about events that can be used to diagnose problems after they have occurred. Logging low-memory conditions, for example, can provide information about a problem that the system administrator can solve by adding more memory to the computer.

Following are more examples in which event logging is helpful:

• A disk driver encounters a bad sector on the disk. It may be able to read from or write to the sector after some retries, but the sector will probably go bad eventually. The disk driver should log a warning if it can proceed; otherwise, it should log an error.

• A file system finds a bad sector and fixes it. A large number of events of this type might indicate that the disk is about to fail. The file system logs a warning event.

• A device driver encounters a hardware problem, such as a disk controller time-out, a power failure in a parallel port, or a data error from a network or serial card. Logging information about these events can help in diagnosing hardware problems. The device driver logs the hardware problem.

• An Application encounters resource problems. An application or a device driver may get into a low-memory situation (caused by a code bug, for example) that degrades performance. Logging an event when memory allocation fails might later provide a clue about what went wrong. The application logs the resource problem.

• A server application (a database or a communications server, for example) records events such as a user logging on, opening a database, or starting a file transfer. The server can also log important information as it runs, such as the number of resources the application is using, errors it encounters (cannot access file, host process disconnected, and so on), a corruption in the database (not able to find a leaf node down a certain path in a tree), or whether a file transfer was successful or not. All of this information can be valuable to a support person (or to the developer of the application). The application records such events and logs them as information events.

Software for developers

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More information resources

MegaDetailed.Net
Unix Manual Pages
Delphi Examples

Databases for Amazon shops developers

Amazon Categories Database
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