|Data Set Options under OpenVMS
Specifies the multibuffer count for a data set.
||2 for files opened for update; 1 for files opened
for input or output
||DATA step and PROC steps
||Data Set Control
||All aspects are host-specific
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
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
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