Service Level Management
Outages¶
An outage is a period of time during which a Monitored Object (i.e., a host or a service) or a Business Process is in a non-available state. In the simplest case, an outage is defined as the period of time between two consecutive available statuses, during which an event takes place, that influences the Availability; the states that affect Availability negatively and that are used for the calculation of outages are HARD events only.
Each Outage has an associated Duration, which is the total amount of time during which the Monitored Object or Business Process was in a non-available state.
During each calculation period, the sum of the duration of all outages plus the duration of Available statuses must equal the duration of the calculation period itself.
Outages appear as part of each SLM report, if configured, and it is possible to configure to show only the number of outages, or a detailed list of outages for each monitored object in the report. It is also possible to include Outage Annotation for every outage, which will then be rendered in the SLM report, if defined. More information can be found in the Outage configuration section.
Whenever the availability is below the required target availability, the monitored host or service is highlighted. You can drill down on any calculation period with an Availability below 100%, to a new page, presenting a detailed report of the related events.
In case an Operational Time has been defined in a SLA, the definition and computation of an outage change slightly. In this case, indeed, Outages are recorded only when they fall within an Operational Time; when the state of non-availability takes place outside an Operational Time, it is called Unavailability Period. In other words, an Unavailability Period is an interval of time during which a service, host, or Business Process is not available and becomes an Outage if it falls at least partially within an Operational Time.
In the remainder of this section, we show examples of how Outages are calculated with Operational time and how they are considered within and across Calculation Periods.
Records of Outages with Operational Time¶
This section enumerates all the basic cases that are taken into account for the calculation of outages, by considering a scenario with one Calculation Period composed of two Operational Time Ranges: the first from 8AM to 9AM and the second from 10AM to 11AM.
More complex scenarios can be reproduced by suitably combining the following cases.
Throughout this section, in all the diagrams and in the text, OT
stands for Operational Time and reports all the Operational Time
Ranges, while UnPs represent Unavailability Periods, i.e., the
intervals during which a host or service is unavailable.
Unavailability Periods outside the Operational Time
7AM 8AM 9AM 10AM 11AM 12AM
|----------|----------|----------|---------|--------|
OT |----------| |---------|
UnPs 1---1 2---2
| |
| \-> 1 outage of 30 minutes
\-> no outage
In this example the Unavailability Period 1 [7:20AM-7:40AM]
starts and ends outside any Operational Time Range, so it causes no
outage.
The Unavailability Period 2 [8AM-8:30AM] instead, falls
completely inside the first Operational Time Range, so it causes an
outage that starts at 8AM and ends at 8:30AM, with a duration of
30min.
Reported Outage:
Outage start: 8AM
Outage end: 8:30AM*
Outage duration: 30min
Unavailability Periods starting or ending outside Operational Times
7AM 8AM 9AM 10AM 11AM 12AM
|----------|----------|----------|---------|--------|
OT |----------| |---------|
UnPs 1---------------------1
|
\-> 1 outage of 1 hour
The UnP 1 [7:30AM-9:30AM] starts before the OT range
[8AM-9AM] and ends after the OT range [8AM-9AM].
Since Outages exist only during the Operational Time, the UnP causes an Outage that starts together with the OT at 8AM, which is the beginning of the OT range [8AM-9AM] and ends at 9AM, which is the end of the OT range [8AM-9AM].
The duration of the Outage is 1h, which is the amount of Operational Time affected by the Outage.
Reported Outage:
Outage start: 8AM
Outage end: 9AM
Outage duration: 1h
Unavailability Periods across different Operational Time ranges
7AM 8AM 9AM 10AM 11AM 12AM
|----------|----------|----------|---------|--------|
OT |----------| |---------|
UnPs 1--------------------------------1
|
\-> 1 single outage of 90 minutes
The UnP 1 [7:30AM-10:30AM] starts before the first OT range
[8AM-9AM], and ends during the second OT range [10AM-11AM].
This means that the Unavailability Period causes an Outage that starts at 8AM (the start of OT range [8AM-9AM]) and ends at 10:30AM, after the second OT range starts. The duration of the Outage is 1h 30min, since the Outage affected the full OT range [8AM-9AM] and the first 30min of the OT range [10AM-11AM].
Reported Outage:
Outage start: 8AM
Outage end: 10:30AM*
Outage duration: 1h 30min
Temporary Uptimes between Operational Time ranges
7AM 8AM 9AM 10AM 11AM 12AM
|----------|----------|----------|---------|--------|
OT |----------| |---------|
UnPs 1---------------------1 2-----------------2
↓ ↓
1 single outage of 2 hours
In this case the UnP 1 [7:20AM-9:20AM] entirely covers the OT
range [8AM-9AM] and the UnP 2 [9:40AM-11:30AM] entirely
covers the subsequent OT range [10AM-11AM].
The resulting Outage is a single Outage that starts at 8AM and ends at 11AM, with a duration of 2h. Only one Outage is reported because during the Operational Time, the Monitored Object or Business Process was continuously unavailable, with the short availability window completely outside the OT. The short interval during which the Monitored Object or Business Process was available [9:20AM-9:40 AM] is disregarded as it is outside the OT.
Reported Outage:
Outage start: 8AM
Outage end: 11AM
Outage duration: 2h
Temporary Uptimes during Operational Time ranges
7AM 8AM 9AM 10AM 11AM 12AM
|----------|----------|----------|---------|--------|
OT |----------| |---------|
UnPs 1----------------1 2----------2
| |
| \-> 1 outage of 30 minutes
\-> 1 outage of 50 minutes
Here the UnP 1 [7:20AM-8:50AM] ends just before the end of the
first OT range [8AM-9AM], and the UnP 2 [9:30AM-10:30AM]
overlaps with the beginning of the second OT range [10AM-11AM].
This causes 2 different Outages, because during both Operational Time Ranges the Monitored Object or Business Process changes status (here, it becomes available). The first Outage starts at 8AM and ens at 8:50AM, with a duration of 50min. The 2nd Outage starts at 10AM and ends at 10:30AM, with a duration of 30min
1st Reported Outage:
Outage start: 8AM
Outage end: 8:50AM*
Outage duration: 50min
2nd Reported Outage:
Outage start: 10AM
Outage end: 10:30AM*
Outage duration: 30min
Unavailability Periods starting or ending on OT range start or end
7AM 8AM 9AM 10AM 11AM 12AM
|----------|----------|----------|---------|--------|
OTs |----------| |---------|
UnPs 1------------------1 2-----------------2
↓ ↓
1 single outage of 2 hours
In case an Unavailability Period starts or ends exactly in the same instant when an OT range starts or ends, then the start or end of the Unavailability Period will be always considered as happening outside the OT range. This case is very similar to the first case presented, with the only difference that two events coincide with the start or end f an Operational Time Range.
The UnP 1 [7:20AM-9AM] ends exactly in the same moment when the
first OT range [8AM-9AM] ends, while UnP 2 [10AM-11:50AM]
starts exactly in the same moment when the second OT range
[10AM-11AM] starts.
This causes a single Outage that starts at 8AM and ends at 11AM, with a duration of 2h.
This happens because the end of UnP 1 [7:20AM-9AM] is considered
as happening after the first OT range [8AM-9AM] and the start of UnP
2 [10AM-11:50AM] is considered as happening before the second OT
range [10AM-11AM]. So the Monitored Object or Business Process was
continuously unavailable for the whole Operational Time.
Reported Outage:
Outage start: 8AM
Outage end: 11AM
Outage duration: 2h
Outages and Calculation Periods.¶
The previous cases take into account Operational Time Ranges, during which the interval between two consecutive Time Ranges is disregarded, so an Unavailability Period that spans multiple OT Ranges is considered as a single Outage.
In this section, we define how Outages are considered when Calculation Periods are taken into account.
The simplest case, when one Unavalability Period (and therefore the Outage) is entirely included in a Calculation Period, results in a single Outage reported in that Calculation Period.
However, when an Unavailability Period spans across two Calculation
Periods, although Calculation Periods are by default contiguous time
intervals, the Outage will be split into two outages, one for the
first Calculation Period, one for the second. The same applies when
multiple Calculation Periods are involved, like the following diagram
shows. Here, CP are Calculation Periods and OUT are the recorded
Outages.
Jan 2020 Feb Mar Apr May June
|----------|----------|----------|---------|--------|
CPs |----------|----------|----------|---------|--------|
UnPs 1-------------1 2----------------------2
OUT |---O1---|-O2-| |--O3--|---O4----|--O5-|
In this example, although there are only two UnP, five Outages will be reported, one for each month in which the Monitored Object or Business Process was not available. In summary (note that the actual Duration in the report will be in HH:MM:SS, here we use days for simplicity), the first Unavailability Period results in:
Reported Outage (January):
Outage start: 7th of January,
Outage end: 31st of January
Outage duration: 25 days
Reported Outage (February):
Outage start: 1st of February
Outage end: 14th of February
Outage duration: 14 days
while the second Unavailability Period results in:
Reported Outage (March):
Outage start: 10th of March
Outage end: 31st of March
Outage duration: 21 days
Reported Outage (April):
Outage start: 1st of April
Outage end: 30th of April
Outage duration: 30 days
Reported Outage (May):
Outage start: 1st of May
Outage end: 19th of may
Outage duration: 19 days
