HDS has a number of internal integer tuning parameters whose values control various aspects of its behaviour and some of which may have an important effect on its performance. Each of these parameters has a default value, but may be over-ridden by either of two mechanisms.
setenv HDS_INALQ 10
could be used to increase the default size of all newly created HDS
files to 10 blocks.
The name of the environment variable is constructed by prefixing the string `HDS_' to the tuning parameter name. All such environment variables must be specified using upper case.
It should be recognised that this ability to set tuning parameter values via environment variables can be dangerous. It is provided mainly to encourage experimentation and to overcome "one-off" tuning problems, but it carries a risk of disrupting normal program behaviour. In particular, you should not expect that all HDS programs will necessarily continue to work with all possible settings of their tuning parameters, and software developers are urged not to write programs which depend on non-default settings of HDS tuning parameters, as this may give rise to conflicts with other software. If a tuning parameter setting really is critical, then it should be set by the software itself (see below), so as to prohibit outside interference.
CALL HDS_TUNE( 'MAP', 0, STATUS )
This would have the effect of disabling file mapping in favour of
reading and writing as the preferred method of accessing data in
container files. The related routine HDS_GTUNE
may be used to determine the current setting of a tuning parameter
(see § for an example of its use).
HDS Hierarchical Data System