Nova Software,Inc.
Network Equipment Performance Monitor

Support for NEPM

Support for NEPM is available from the following sources:
NEPM: Knowledge Base/FAQ

NEPM: Knowledge Base

Find your desired entry in this knowledge base quickly by using your browser's 'find' or 'search' function, often found under the 'Edit' menu, or click on a topic in the table of contents to browse in it.


Leap days are not counted when dates are more than 10 months apart. (LE020315)
This effect will produce a maximum error of 0.3%, and generally much less.



Existing web page detail reports are only overwritten by a new Builder run, not deleted. (LE020319)
New reports overwrite previous ones of the same name. If the configuration of detail reports has changed since the last run, reports which are no longer run will remain and may be able to be accessed by opening the directory containing them in a browser window. Summary reports are always written on each run, overwriting any earlier ones, so previous detail reports will not be listed in summaries.

Report pages can be taken off-line as a set and still link to one another. (LE020206)
Links between reports are relative, not absolute. If reports are copied to a local directory their encompassing directory structure must also be copied for summary <=> detail links to continue to work. This feature makes it possible to work with an entire set of reports off-line and avoids exporting absolute urls to secure directory sections. .

Duplicate event links may occur in precursor files. (LE020206)
Multiple events with the same time stamp can (rarely) occur in the precursor file, since 1 second is typically the the minimum time resolution provided by most logging software. A link from the event detail reports to the event precursor listing will take you to the first of these event groups in such a case. Check the following event groups, too, to be certain of finding the correct group of 9 precursor events for the one you are linking from.

Reports are rebuilt fully on each Builder run (LE041206)
The reports are fully rebuilt by the Builder on each data run from the latest files and from data hashes saved on disk representing all earlier data within the current data age setting. If some files are missing on a particular data run no results for those files will be output for that run, but all historical data is retained on disk in Builder's data directory. Re-running with a successful capture of those files will output the full set of reports again. Normally no data is lost if capture runs are frequent enough.



Time inversions at startup (LE030310)
Operating systems (notably Linux) may adjust the system clock during boot. If the system has experienced substantial positive hardware clock drift while down, the correction can cause some elements to appear to have an earlier boot time than the system itself. As an example Linux adjusts its system time after syslog startup but before starting Apache. If the adjustement moves the time far enough back, the start time shown for Apache in the NEPM downtime summary will apparently preceed that for the system. This effect generally will occur only during extended periods of downtime on systems with severe hardware clock runout.



Two consecutive stop events are assumed never to occur. (LE020206)
NEPM LE assumes that two consecutive stop events (i.e. without an intervening start event) cannot occur. Such a sequence would be impossible in normal operation since a 'start' event is typically the startup of logging, and so gets recorded. This situation might occur if a section of a log with the start event is missing for some reason. Such occurrences should be extremely rare.

Clear (delete) existing master data files when adding events to the Builder control file event messages list. (LE020206)
Results are undefined if additional event types are added to existing master data files.

Clear (delete) existing master data files when adding an earlier log to a sequence to be captured. (LE020206)
The master data files keep a time record of files captured. Attempting to add an earlier file to an existing record will produce unpredictable results, and is not supported. Simply delete the existing data files and start fresh with the complete set of files to be captured, including the one you wish to add.

Breaks larger than 24 hours between the last event of one file and the first of the next are reported. (LE020213)
If the start time of a new file is within one day of the previous files' endtime we assume that any gap is due to lack of events, not a missing file or off system. Conversely, beyond 24 hours we make the opposite assumption and record a gap in the event monitoring. If a large enough percentage of the total monitoring time, these gaps are reported.



Performance graphs do not display a partial last bin. (LE020206)
Each performance graph uses a fixed time bin of your choosing. If this period is, say, one hour, and the input log file does not contain an integer number of hours of data, the last bin will represent only a portion of an hour. To avoid inaccuracy this bin of data is not displayed.



Threshold start time and duration may vary between file sets. (LE020206)
Threshold start time and duration stated in the alert email and on the alerts web page refer to the last file set to be captured and analyzed. Prior file sets in the run may have slightly different times. The differences are generally a few percent at most.


Control Files

Multiple log files with an element group must be captured by the Courier in chronological order. (LE020206)
This is controlled very simply by the order in which they are listed in the Courier's control file. More detail is provided in the Courier's control file's internal notes, and in the User Guide.

System type in the Courier control file must match that in Builder's 'messages' sub-file. (LE020206)
Use 'Unix' to denote most systems of this general type or 'WinNT' for Windows NT 4.0 or 5.0 (2000). All releases to date of NEPM have only been tested and verified to correctly monitor target systems based on one of these two types of OS's. For other systems contact Nova Software at

Log files of the same origin are assumed to have a common root name. (LE020206)
It is assumed that files reporting the same type of results for an element, and just differing in the time period covered all have the same root name and differ only due to appended numbers. E.g. messages, messages.1 or nc020202.log, nc020203.log, etc. Filesets which do not follow this convention will not produce correct results.



Long delay between connecting and receiving a login request from Linux. (LE0202006)
In rare cases the Courier may experience a long delay (up to three minutes) between connecting to a remote Telnet server on Linux and receiving its login request. This problem is caused by DNS mis-configuration on some Linux systems: The server is waiting for a reverse DNS lookup of the domain of the remote client's host. The lookup never succeeds and times out instead, causing the long delay. A quick fix is to add the Courier hostname and domain to /etc/hosts on the target system (and confirm that its /etc/hosts file is configured as part of the DNS lookup process.) Alternatively add the Courier's hostname and domain to a local DNS resolver accessed by the affected system.

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