Chapter 3. Understanding Logging
Both of the Informix engines keep track of changes to its data by the use of logfiles. There are two types of logfiles, physical and logical. Each logfile is accessed through buffers in the shared memory. You need to make the distinction between the log buffers, which are areas of shared memory and the logfiles, which are areas of the disk that receive data from the buffers. The shared memory is by definition transitory. If the system goes down, this data is lost. The logfiles on disk are persistent. Assuming there are no hardware problems with the disk, their contents survive system crashes.
The essential point of difference between the physical and logical logs is really indicated by their names. The physical ...
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