How to
Editing the Log Size for a Trend Log
You increase or decrease the number of records to be stored in the trend log before records are overwritten.
All trend logs use circular storing. How many records a trend log can store before overwriting old ones depends on the trend log configuration.
For example, a trend log is configured to store 10 records. The logging starts and the first record x1 is stored. After 10 records the trend log is full. The next record x11 overwrites the oldest record which in our case is x1. The next logging x12 overwrites the oldest record x2, and so on.
Additional internal records can be generated by the log itself. These records may not be visible. Internal records are a part of the log usage.
If you try to configure a trend log to store a larger number of log records than the EcoStruxure BMS server can manage, the trend log is not created.
Circular storing, schematic
In WorkStation, in the System Tree pane, click the trend log whose log size you want to edit.
In the Extended Trend Log properties, in the Log size box, enter the new value.
Click the Save button
.action_zoom_plus_stroke 
Configuring an Extended Trend Log
Extended Trend Log Properties – Basic Tab
Log Record Storage