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Data Set Options under OpenVMS

MBF= Data Set Option: OpenVMS

Specifies the multibuffer count for a data set.
Default: 2 for files opened for update; 1 for files opened for input or output
Valid in: DATA step and PROC steps
Category: Data Set Control
Engines: CONCUR
OpenVMS specifics: All aspects are host-specific

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is the number of I/O buffers that you want OpenVMS RMS to allocate for a particular file. The value can range from 0 to 127, and it must be an integer. If you specify MBF=0, the process's default value is used.


A multibuffer count of 1 is adequate to process your data set sequentially. However, for random access, it is more efficient to use more than one buffer to store various parts of your file in memory. For example, to tell OpenVMS RMS to allocate five buffers for every file in a data library, use the following statement:

libname test concur '[mydir]' mbf=5;

The MBF= data set option corresponds to the FAB$B_MBF field in OpenVMS RMS or to the CONNECT MULTIBUFFER_COUNT attribute when you are using FDL. For additional details about the FAB$B_MBF field, see Guide to OpenVMS File Applications.

See Also

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