IP_hTASK historian, char* retbuf, int buflen, char* histpattern
The task pointer to the Cascade Historian program.
An optional buffer containing an error message.
The length in bytes of retbuf. If retbuf is non-NULL, this must be a valid non-zero length. If retbuf is NULL, this parameter is ignored.
A globbing pattern specifying a group of histories.
ST_OK on success. Otherwise ST_ERROR, and the retbuf will contain a NULL-terminated character string with an error message. If the return value is ST_OK, the retbuf may not contain useful information.
This function causes the Cascade Historian to unregister each history matching the pattern from the Cascade DataHub. The history will cease to receive exceptions when the point value data changes. If multiple histories are associated with the same point, registering or unregistering one of the histories will do the same to all the other histories sharing the same point.
If the history is not currently registered with the Cascade DataHub, this function does nothing.
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