Connected: An Internet Encyclopedia
3.1. The Alarm Group

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3.1. The Alarm Group

3.1. The Alarm Group

   -- the alarm group
   --
   -- a collection of objects allowing the description and
   -- configuration of threshold alarms from a SNMPv2 entity
   -- acting in a dual role.

   snmpAlarm      OBJECT IDENTIFIER ::= { snmpM2MObjects 1 }

   -- This Alarm mechanism periodically takes statistical samples
   -- from variables available via SNMPv2 and compares them to
   -- thresholds that have been configured.  The alarm table
   -- stores configuration entries that each define a variable,
   -- polling period, and threshold parameters.  If a sample is
   -- found to cross the threshold values, an event is generated.
   -- Only variables that resolve to an ASN.1 primitive type of
   -- INTEGER (Integer32, Counter32, Gauge32, TimeTicks,
   -- Counter64, or UInteger32) may be monitored in this way.
   --
   -- This function has a hysteresis mechanism to limit the
   -- generation of events.  This mechanism generates one event
   -- as a threshold is crossed in the appropriate direction.  No
   -- more events are generated for that threshold until the
   -- opposite threshold is crossed.
   --
   -- In the case of sampling a deltaValue, an entity may
   -- implement this mechanism with more precision if it takes a
   -- delta sample twice per period, each time comparing the sum
   -- of the latest two samples to the threshold.  This allows
   -- the detection of threshold crossings that span the sampling
   -- boundary.  Note that this does not require any special
   -- configuration of the threshold value.  It is suggested that
   -- entities implement this more precise algorithm.
   --

   snmpAlarmNextIndex OBJECT-TYPE
       SYNTAX     INTEGER (0..65535)
       MAX-ACCESS read-only
       STATUS     current
       DESCRIPTION
               "The index number of the next appropriate
               unassigned entry in the snmpAlarmTable.  The value
               0 indicates that no unassigned entries are
               available.

               A management station should create new entries in
               the snmpAlarmTable using this algorithm: first,
               issue a management protocol retrieval operation to
               determine the value of snmpAlarmNextIndex; and,
               second, issue a management protocol set operation
               to create an instance of the snmpAlarmStatus
               object setting its value to `createAndGo' or
               `createAndWait' (as specified in the description
               of the RowStatus textual convention)."
       ::= { snmpAlarm 1 }

   snmpAlarmTable OBJECT-TYPE
       SYNTAX     SEQUENCE OF SnmpAlarmEntry
       MAX-ACCESS not-accessible
       STATUS     current
       DESCRIPTION
               "A list of snmpAlarm entries."
       ::= { snmpAlarm 2 }

   snmpAlarmEntry OBJECT-TYPE
       SYNTAX     SnmpAlarmEntry
       MAX-ACCESS not-accessible
       STATUS     current
       DESCRIPTION
               "A list of parameters that set up a periodic
               sampling query to check for alarm conditions.  The
               contextIdentity included in the INDEX clause is
               the context to which the sampling queries are
               directed."
       INDEX      { contextIdentity, snmpAlarmIndex }
       ::= { snmpAlarmTable 1 }

   SnmpAlarmEntry ::= SEQUENCE {
       snmpAlarmIndex                    INTEGER,
       snmpAlarmVariable                 InstancePointer,
       snmpAlarmInterval                 Integer32,
       snmpAlarmSampleType               INTEGER,
       snmpAlarmValue                    Integer32,
       snmpAlarmStartupAlarm             INTEGER,
       snmpAlarmRisingThreshold          Integer32,
       snmpAlarmFallingThreshold         Integer32,
       snmpAlarmRisingEventIndex         INTEGER,
       snmpAlarmFallingEventIndex        INTEGER,
       snmpAlarmUnavailableEventIndex    INTEGER,
       snmpAlarmStatus                   RowStatus
   }

   snmpAlarmIndex OBJECT-TYPE
       SYNTAX     INTEGER (1..65535)
       MAX-ACCESS not-accessible
       STATUS     current
       DESCRIPTION
               "An index that uniquely identifies an entry in the
               snmpAlarm table for a particular sampling context.
               Each such entry defines a diagnostic sample at a
               particular interval for a variable in the
               particular context's object resources."
       ::= { snmpAlarmEntry 1 }

   snmpAlarmVariable OBJECT-TYPE
       SYNTAX     InstancePointer
       MAX-ACCESS read-create
       STATUS     current
       DESCRIPTION
               "The object identifier of the particular variable
               to be sampled.  Only variables that resolve to an
               ASN.1 primitive type of INTEGER (Integer32,
               Counter32, Gauge32, TimeTicks, Counter64, or
               UInteger32) may be sampled.

               If it is detected by an error response of
               authorizationError, noSuchObject, or
               noSuchInstance that the variable name of an
               established snmpAlarmEntry is no longer available
               in the sampling context, a single
               snmpObjectUnavailableAlarm event is generated and
               the status of this snmpAlarmEntry is set to
               `destroy'.  Likewise, if the syntax of the
               variable retrieved by the query is not Integer32,
               Counter32, Gauge32, TimeTicks, Counter64, or
               UInteger32, the same actions will be taken.

               If the SNMPv2 entity acting in a dual role detects
               that the sampled value can not be obtained due to
               lack of response to management queries, it should
               either:

                    1) Set the status of this snmpAlarmEntry to
                    `destroy', if it is determined that further
                    communication is not possible;

                    or,

                    2) Delete the associated snmpAlarmValue
                    instance (but not the entire conceptual row),
                    and continue to attempt to sample the
                    variable and recreate the associated
                    snmpAlarmValue instance should communication
                    be reestablished.

               An attempt to modify this object will fail with an
               `inconsistentValue' error if the associated
               snmpAlarmStatus object would be equal to `active'
               both before and after the modification attempt."
       ::= { snmpAlarmEntry 2 }

   snmpAlarmInterval OBJECT-TYPE
       SYNTAX     Integer32
       UNITS      "seconds"
       MAX-ACCESS read-create
       STATUS     current
       DESCRIPTION
               "The interval in seconds over which the data is
               sampled and compared with the rising and falling
               thresholds.  When setting this object and the
               sampling type is `deltaValue',  care should be
               taken to ensure that the change during this
               interval of the variable being sampled will not
               exceed the (-2^31...2^31-1) range of the
               snmpAlarmValue.

               An attempt to modify this object will fail with an
               `inconsistentValue' error if the associated
               snmpAlarmStatus object would be equal to `active'
               both before and after the modification attempt."
       ::= { snmpAlarmEntry 3 }

   snmpAlarmSampleType OBJECT-TYPE
       SYNTAX     INTEGER {
                      absoluteValue(1),
                      deltaValue(2)
                  }
       MAX-ACCESS read-create
       STATUS     current
       DESCRIPTION
               "The method of sampling the selected variable and
               calculating the value to be compared against the
               thresholds.  If the value of this object is
               `absoluteValue', the value of the selected
               variable at the end of the sampling interval will
               be compared directly with both the
               snmpAlarmRisingThreshold and the
               snmpAlarmFallingThreshold values.  If the value of
               this object is `deltaValue', the value of the
               selected variable at the end of the sampling
               interval will be subtracted from its value at the
               end of the previous sampling interval, and the
               difference compared with both the
               snmpAlarmRisingThreshold and the
               snmpAlarmFallingThreshold values.

               An attempt to modify this object will fail with an
               `inconsistentValue' error if the associated
               snmpAlarmStatus object would be equal to `active'
               both before and after the modification attempt."
       DEFVAL { deltaValue }
       ::= { snmpAlarmEntry 4 }

   snmpAlarmValue OBJECT-TYPE
       SYNTAX     Integer32
       MAX-ACCESS read-only
       STATUS     current
       DESCRIPTION
               "The value of the statistic during the last
               sampling period.  The value during the current
               sampling period is not made available until the
               period is completed.  If the value of the
               statistic does not fit in the signed 32 bit
               representation of this object, it should be
               truncated in an implementation specific manner.

               Note that if the associated snmpAlarmSampleType is
               set to `deltaValue', the value of this object is
               the difference in the sampled variable since the
               last sample.

               This object will be created by the SNMPv2 entity
               acting in a dual role when this entry is set to
               `active', and the first sampling period has
               completed.  It may be created and deleted at other
               times by the SNMPv2 entity acting in a dual role
               when the sampled value can not be obtained, as
               specified in the snmpAlarmVariable object."
       ::= { snmpAlarmEntry 5 }

   snmpAlarmStartupAlarm OBJECT-TYPE
       SYNTAX     INTEGER {
                      risingAlarm(1),
                      fallingAlarm(2),
                      risingOrFallingAlarm(3)
                  }
       MAX-ACCESS read-create
       STATUS     current
       DESCRIPTION
               "The alarm that may be sent when this entry is
               first set to `active'.  If the first sample after
               this entry becomes active is greater than or equal
               to the risingThreshold and snmpAlarmStartupAlarm
               is equal to `risingAlarm' or
               `risingOrFallingAlarm', then a single rising alarm
               will be generated.  If the first sample after this
               entry becomes active is less than or equal to the
               fallingThreshold and snmpAlarmStartupAlarm is
               equal to `fallingAlarm' or `risingOrFallingAlarm',
               then a single falling alarm will be generated.
               Note that a snmpObjectUnavailableAlarm is sent
               upon startup whenever it is applicable,
               independent of the setting of
               snmpAlarmStartupAlarm.

               An attempt to modify this object will fail with an
               `inconsistentValue' error if the associated
               snmpAlarmStatus object would be equal to `active'
               both before and after the modification attempt."
       DEFVAL { risingOrFallingAlarm }
       ::= { snmpAlarmEntry 6 }

   snmpAlarmRisingThreshold OBJECT-TYPE
       SYNTAX     Integer32
       MAX-ACCESS read-create
       STATUS     current
       DESCRIPTION
               "A threshold for the sampled statistic.  When the
               current sampled value is greater than or equal to
               this threshold, and the value at the last sampling
               interval was less than this threshold, a single
               event will be generated.  A single event will also
               be generated if the first sample after this entry
               becomes active is greater than or equal to this
               threshold and the associated snmpAlarmStartupAlarm
               is equal to `risingAlarm' or
               `risingOrFallingAlarm'.

               After a rising event is generated, another such
               event will not be generated until the sampled
               value falls below this threshold and reaches the
               snmpAlarmFallingThreshold.

               An attempt to modify this object will fail with an
               `inconsistentValue' error if the associated
               snmpAlarmStatus object would be equal to `active'
               both before and after the modification attempt."
       ::= { snmpAlarmEntry 7 }

   snmpAlarmFallingThreshold OBJECT-TYPE
       SYNTAX     Integer32
       MAX-ACCESS read-create
       STATUS     current
       DESCRIPTION
               "A threshold for the sampled statistic.  When the
               current sampled value is less than or equal to
               this threshold, and the value at the last sampling
               interval was greater than this threshold, a single
               event will be generated.  A single event will also
               be generated if the first sample after this entry
               becomes active is less than or equal to this
               threshold and the associated snmpAlarmStartupAlarm
               is equal to `fallingAlarm' or
               `risingOrFallingAlarm'.

               After a falling event is generated, another such
               event will not be generated until the sampled
               value rises above this threshold and reaches the
               snmpAlarmRisingThreshold.

               An attempt to modify this object will fail with an
               `inconsistentValue' error if the associated
               snmpAlarmStatus object would be equal to `active'
               both before and after the modification attempt."
       ::= { snmpAlarmEntry 8 }

   snmpAlarmRisingEventIndex OBJECT-TYPE
       SYNTAX     INTEGER (0..65535)
       MAX-ACCESS read-create
       STATUS     current
       DESCRIPTION
               "The index of the snmpEventEntry that is used when
               a rising threshold is crossed.  The snmpEventEntry
               identified by a particular value of this index is
               the same as identified by the same value of the
               snmpEventIndex object.  If there is no
               corresponding entry in the snmpEventTable, then no
               association exists.  In particular, if this value
               is zero, no associated event will be generated, as
               zero is not a valid snmpEventIndex.

               An attempt to modify this object will fail with an
               `inconsistentValue' error if the associated
               snmpAlarmStatus object would be equal to `active'
               both before and after the modification attempt."
       ::= { snmpAlarmEntry 9 }

   snmpAlarmFallingEventIndex OBJECT-TYPE
       SYNTAX     INTEGER (0..65535)
       MAX-ACCESS read-create
       STATUS     current
       DESCRIPTION
               "The index of the snmpEventEntry that is used when
               a falling threshold is crossed.  The
               snmpEventEntry identified by a particular value of
               this index is the same as identified by the same
               value of the snmpEventIndex object.  If there is
               no corresponding entry in the snmpEventTable, then
               no association exists.  In particular, if this
               value is zero, no associated event will be
               generated, as zero is not a valid snmpEventIndex.

               An attempt to modify this object will fail with an
               `inconsistentValue' error if the associated
               snmpAlarmStatus object would be equal to `active'
               both before and after the modification attempt."
       ::= { snmpAlarmEntry 10 }

   snmpAlarmUnavailableEventIndex OBJECT-TYPE
       SYNTAX     INTEGER (0..65535)
       MAX-ACCESS read-create
       STATUS     current
       DESCRIPTION
               "The index of the snmpEventEntry that is used when
               a variable becomes unavailable.  The
               snmpEventEntry identified by a particular value of
               this index is the same as identified by the same
               value of the snmpEventIndex object.  If there is
               no corresponding entry in the snmpEventTable, then
               no association exists.  In particular, if this
               value is zero, no associated event will be
               generated, as zero is not a valid snmpEventIndex.

               An attempt to modify this object will fail with an
               `inconsistentValue' error if the associated
               snmpAlarmStatus object would be equal to `active'
               both before and after the modification attempt."
       ::= { snmpAlarmEntry 11 }

   snmpAlarmStatus OBJECT-TYPE
       SYNTAX     RowStatus
       MAX-ACCESS read-create
       STATUS     current
       DESCRIPTION
               "The status of this snmpAlarm entry.  This object
               may not be set to `active' unless the following
               columnar objects exist in this row:
               snmpAlarmVariable, snmpAlarmInterval,
               snmpAlarmSampleType, snmpAlarmStartupAlarm,
               snmpAlarmRisingThreshold,
               snmpAlarmFallingThreshold,
               snmpAlarmRisingEventIndex,
               snmpAlarmFallingEventIndex, and
               snmpAlarmUnavailableEventIndex."
       ::= { snmpAlarmEntry 12 }


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Connected: An Internet Encyclopedia
3.1. The Alarm Group