installation

product features

what is the relationship with other mv databases?

product licensing

how do release numbers work?

what is a dynamic file?

keyboard input problems

qmserver problems

the qmclient api

security issues

can i sell my own qm applications?

terminal support

what is a dynamic file?

dynamic files are used to store most data in qm applications. they employ a hashing process to locate records by a mathematical transformation of the record id to a file position. the aim is that a record can be located with just a single disk access regardless of whether the file contains 10 records or 10 million records. in reality, a small proportion of the records in a file may take more than one disk access but the average should be very close to one.

most high performance file systems need periodic retuning to maintain their performance as the data in the files changes. this usually requires users to be logged off the system for some time. dynamic files are automatically restructured in very small steps during normal use, effectively spreading the cost of retuning very thinly over the normal operation of the file.

although there are configuration parameters that can be used to adjust the way in which dynamic files work, most users simply leave them at their defaults and let the system sort itself out.

for more information about the inner workings of dynamic files, visit the technical notes page for a detailed description.