ihAlarms Table

The ihAlarms table contains collected alarms and events data. The following table describes the columns of the ihAlarms table.

CAUTION: When you perform joins of the ihRawData and ihAlarms tables, you can easily construct queries that temporarily consume all your system resources. Although this scenario typically does not affect data collection, it can interfere with data analysis. To avoid this issue, always define a start and end time for the query to limit the number of rows returned.

Table 1. ihAlarms Table
Column Name	Data Type	Description
`AlarmID`	`VT_I4`	The unique ID of the alarm or event in the Historian alarm database.
`ItemID`	`VT_BSTR`	The OPC `ItemID` of the alarm. This contains the source address of the data access tag with which the alarm is associated. This can contain a `NULL` value if an alarm is not associated with a tag.
`Source`	`VT_BSTR`	The unique identifier used by the OPC AE Collector for the alarm or event.
`DataSource`	`VT_BSTR`	The collector interface name associated with the alarm or event.
`Tagname`	`VT_BSTR`	The Historian tag name associated with the alarm. This value is `NULL` unless the tag is also collected by Historian.
`AlarmType`	`VT_BSTR`	The alarm type: `Alarms`: In Historian, the full life cycle of an alarm is stored as a single record in the alarm archive. `Alarm_History`: The separate transitions for all alarms. One row per transition is returned. `Events`: The simple and tracking events.
`EventCategory`	`VT_BSTR`	The OPC event category of the alarm or event.
`Condition`	`VT_BSTR`	The OPC condition of the alarm. Does not apply to event data. This value combined with the `Source` value comprises an alarm.
`SubCondition`	`VT_BSTR`	The OPC subcondition of the alarm. Does not apply to event data. This value represents the state of the alarm.
`StartTime`	`VT_DBTimeStamp`	The start time or timestamp of the alarm or event.
`EndTime`	`VT_DBTimeStamp`	The end time of the alarm. Does not apply to event data.
`AckTime`	`VT_DBTimeStamp`	The time the alarm was acknowledged. Does not apply to event data.
`Microseconds`	`VT_I4`	The microsecond portion of the date and time.
`Message`	`VT_BSTR`	The message attached to the alarm or event.
`Acked`	`VT_BOOL`	Stores the acknowledgement status of the alarm. If the alarm is acknowledged, this is set to `TRUE`.
`Severity`	`VT_I4`	The severity of the alarm or event. Stored as an integer value with a range of 1–1000.
`Actor`	`VT_BSTR`	The operator who acknowledged the alarm, or caused the tracking event.
`Quality`	`VT_VARIANT`	The quality of the alarm or event. Stored as a string, with values of `GOOD` or `BAD`.
`TimeZone`	`VT_BSTR`	The type of time zone used: Client Server Explicit bias number (number of minutes from GMT)
`DaylightSavingTime`	`VT_BOOL`	Indicates whether Daylight Saving Time logic should be applied to timestamps.
`RowCount`	`VT_I4`	The maximum number of rows returned by the current query.
`User-Defined Variable #X`	`VT_VARIANT`	User-defined variables. This is a dynamic list of columns that varies based on the collectors running on the Historian system.

Note: Additional fields may be added by third-party products such as iFIX. Please consult the relevant product documentation for further information.

ihAlarms Examples

Example 1: Show All Alarms for the Last Two Hours, Including Vendor Attributes

SELECT * FROM ihAlarms
SELECT * FROM ihAlarms WHERE alarmtype = alarms //same as above

Example 2: Show Alarm History

SELECT * FROM ihAlarms WHERE alarmtype = alarm_history

Example 3: Show Tracking and System Events

SELECT * FROM ihAlarms WHERE alarmtype = events

Example 4: Return All Closed Events and Associated Tag Data

SELECT
alarmid, ihalarms.tagname, ihalarms.starttime, ihalarms.endTime, ihrawdata.timestamp, ihrawdata.value
FROM ihalarms, ihrawdata
WHERE ihalarms.tagname=ihrawdata.tagname
AND ihalarms.starttime <= ihrawdata.timestamp
AND ihalarms.endtime >= ihRawdata.timestamp
AND ihalarms.subcondition == "OK"
OR ihalarms.quality = "Bad"
ORDER BY ihalarms.starttime

Note: When you join data from the ihRawData and ihAlarms tables, be sure to specify a timestamp range.

Example 5: Return All Open Alarms and Associated Tag Data

SELECT
alarmid, ihalarms.tagname, ihalarms.starttime, ihalarms.endTime, ihrawdata.timestamp, ihrawdata.value
FROM ihalarms, ihrawdata
WHERE ihalarms.tagname=ihrawdata.tagname
AND ihalarms.starttime <= ihrawdata.timestamp
AND ihalarms.endtime >= ihRawdata.timestamp
AND ihalarms.subcondition <> "OK"
AND ihalarms.quality = "Good"
ORDER BY ihalarms.starttime

Note: When you join data from the ihRawData and ihAlarms tables, be sure to specify a timestamp range.