15.9. Database management systems' requirements on operating systems
When a system which must provide transactions (such as a DBMS) is implemented above a general-purpose OS, the following must be considered:
the file buffer management policy of the OS;
the concurrency control facilities provided by the OS.
When the DBMS makes a file-write request, and the OS says 'done', the data must have been written to persistent memory. It is not sufficient for the data to get as far as an OS buffer in volatile main memory. A crash could occur and the data could be lost. In the meantime, the DBMS has told its client that the operation is committed and has no means of effecting this.
As we saw in Chapter 6, a file management system provides facilities for ...
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