Computer data logging
Encyclopedia
Computer data logging is the process of recording events, with an automated computer program, in a certain scope in order to provide an audit trail that can be used to understand the activity of the system and to diagnose problems.
Logs are essential to understanding the activities of complex systems particularly in the case of applications with little user interaction (such as server
applications).
It can also be useful to combine log file entries from multiple sources. This approach, in combination with statistical analysis, may yield correlations between seemingly unrelated events on different servers. Other solutions employ network-wide querying and reporting.
systems, and black box recorder
s installed in aircraft.
Many operating systems and multitudinous computer programs include some form of logging subsystem.
In the simplest case, log messages are written to a log file. Most operating systems and software framework
s also provide more sophisticated services for logging. One example is the syslog
service (described in RFC 3164), which allows the filtering and recording of log messages to be performed by a separate dedicated subsystem, rather than placing the onus on each application to provide its own ad hoc logging system.
s maintain some kind of transaction log. Unlike the logs described above, these logs are not mainly intended as an audit trail for later analysis, and are not (easily) human-readable
. Instead, they record changes to the stored data to allow the database to recover from crashes or other errors and maintain the stored data in a consistent state.
Most database systems have both a log in the general sense described above, and a transaction log.
Logs are essential to understanding the activities of complex systems particularly in the case of applications with little user interaction (such as server
Server (computing)
In the context of client-server architecture, a server is a computer program running to serve the requests of other programs, the "clients". Thus, the "server" performs some computational task on behalf of "clients"...
applications).
It can also be useful to combine log file entries from multiple sources. This approach, in combination with statistical analysis, may yield correlations between seemingly unrelated events on different servers. Other solutions employ network-wide querying and reporting.
Examples
Examples of physical systems which have logging subsystems include process controlProcess control
Process control is a statistics and engineering discipline that deals with architectures, mechanisms and algorithms for maintaining the output of a specific process within a desired range...
systems, and black box recorder
Flight data recorder
A flight data recorder is an electronic device employed to record any instructions sent to any electronic systems on an aircraft. It is a device used to record specific aircraft performance parameters...
s installed in aircraft.
Many operating systems and multitudinous computer programs include some form of logging subsystem.
In the simplest case, log messages are written to a log file. Most operating systems and software framework
Software framework
In computer programming, a software framework is an abstraction in which software providing generic functionality can be selectively changed by user code, thus providing application specific software...
s also provide more sophisticated services for logging. One example is the syslog
Syslog
Syslog is a standard for computer data logging. It allows separation of the software that generates messages from the system that stores them and the software that reports and analyzes them...
service (described in RFC 3164), which allows the filtering and recording of log messages to be performed by a separate dedicated subsystem, rather than placing the onus on each application to provide its own ad hoc logging system.
Interpreting
In many cases, logs are esoteric or too verbose and therefore hard to understand; they need to be subjected to log analysis in order to make sense of them. This is often done using special log analysis software.Transaction log
Most DatabaseDatabase
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...
s maintain some kind of transaction log. Unlike the logs described above, these logs are not mainly intended as an audit trail for later analysis, and are not (easily) human-readable
Human-readable
A human-readable medium or human-readable format is a representation of data or information that can be naturally read by humans.In computing, human-readable data is often encoded as ASCII or Unicode text, rather than presented in a binary representation...
. Instead, they record changes to the stored data to allow the database to recover from crashes or other errors and maintain the stored data in a consistent state.
Most database systems have both a log in the general sense described above, and a transaction log.