This view displays activity in the ZODB over a period of time. It shows how many objects were loaded and stored. You can use this information to determine the optimal memory cache size for your Zope application. You can also use it to discover applications that write to the database too often.
Show current chart
The chart contains a bar graph. The rightmost bar shows the most recent activity. The red portion indicates the number of objects stored and the blue portion indicates the number of objects loaded during that time period. To the right of the graph there is a total.
If you click on a bar, the chart will zoom in on the time period for just that bar. You will see the details of the activity during that short time period. Click the "Show current chart" button to return to the chart for the current time.
Once Zope has loaded enough objects, the ZODB cache consistently keeps in the cache the number of objects you specify under the "Cache Parameters" tab. Because the cache size is so consistent and ZODB is so transparent to both the user and application developer, Zope applications can invisibly develop a performance problem by loading objects from ZODB on every request.
Also, if the cache size is set too high, Zope will consume more RAM than it needs. You need to find a good balance that fits your site. If the bar chart shows a large number of objects being loaded all the time, increase the cache size, which will increase memory usage but should also increase performance. If the chart shows little activity even though the site is visited frequently, you can reduce the cache size so Zope will consume less RAM.
As your site changes, its cache size requirements may change also, so remember to make adjustments over time.
If the graph shows a lot of writes (a significant portion of red), some application or product may be writing to the database too frequently. Check the "undo" log for clues. Note that the activity graph does not show activity in mounted databases, so objects loaded and stored by the sessioning machinery are not counted in the graph.