hist_unregister

Cascade Historian: Version 4.1
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# `hist_unregister`

`hist_unregister` -- unregisters histories with the Cascade DataHub.

## Syntax

    hist_unregister (hist_task[, pattern])

## Parameters

`hist_task`

  The task object corresponding to the Cascade Historian. See `locate_task` in the Gamma manual.

`pattern`

  The name of one or more (using a globbing pattern) histories to be acted upon. When this parameter is not specified, the default is `*`, to include all histories.

## Returns

`t` (true) if successful. Otherwise returns `nil` and sets `_last_error_` to the error string returned by the Cascade Historian.

## Description

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.

This function corresponds to the unregister command, and the Cogent API function `HI_Unregister`.

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