When monitoring for activity, you will want to scan as often as possible. This means you will accumulate many traces over the course of a few days. Vision trace databases are limited in the number of traces they will hold. This limitation is in place so that Vision can be responsive to user interaction. Each time you click a different channel or monitor in Vision, all of the traces for that channel are loaded, a spectrogram is generated and other work takes place behind the scenes. If the database is too large, it will become sluggish.

So Vision limits the number of traces to around 10,000 per channel in each database. If you are storing a trace every two seconds, then you reach the 10,000 trace limit in about 5 hours. If you want to collect for several days to thoroughly map out the usage, then you will need to store trace data in multiple databases.

Set Vision Acquire to automatically archive trace tables at regular intervals. To do so, click the Automatically archive trace tables check box. You will also want to set a time interval for doing the automatic archive. Do so in the “Archive every” drop-down list. If you set the Archive to every 6 hours, at intervals the database will be copied to a sub-folder, and the active trace tables will be cleared for storage for the next 6 hour period. The periods have fixed start and stop times. If you set it for 6 hours, then the database will be archived at 6:00 am, noon, 6:00 pm and mid-night each day while it is running. If you start at 10:00 am, then the first archive will only have two hours of data.

As each trace is collected, it is tested against a limit line mask. If the trace exceeds the mask, that trace is marked as having failed. At the end of each run, a report is generated listing each channel that failed. Depending on settings, the database may store weeks or months of trace data, so the report also includes sections for channels that have failed in the past hour, the past day, the past week, and the past month. Users who want to be notified can register to receive this report by email suing the Email Notification system. See Setting Up Email Notifications.

There is also a contact for each probe individually, and an email can be sent just for that probe when it has a channel failure. The user interface provides a table where contacts are registered and the level of reporting is indicated by checking a box. There is also a check box that enables sending emails. If this is not checked, no emails will go out.

There are several database maintenance features available through the UI. If the check box is clear for removing old traces, then nothing will get automatically removed and the trace tables will continue to store old data and grow very large. Keep in mind that a typical installation with 1,000 probes will store 12,000 traces 4 times an hour. Using rough numbers, that is 50,000 traces per hour, or 1.2 million traces a day. If you store 30 days of data, that is almost 40 million traces in the database. Each trace takes around 4,000 bytes, so we have 160 Gigabytes of data. If you let that go several months without removing old traces, it can become quite large and unwieldy, potentially exceeding space available and certainly affecting system speed and responsiveness.

Trace mask violations will result in a reported failure. The very first email-generated report that is issued will always show 1 fail count for each channel reported on in the notification. This failure report is generated shortly after starting trace capture in Vision Acquire regardless of the frequency specified in the notification settings.

Subsequent email reports reflect the actual failed trace totals. The first report counts 1 per channel as shown in the Vision Failure Report example below in Figure: Trace Mask Failure Report.