Technically if you are running low on memory your call logs and SMS logs will be automatically deleted. Are you synchronizing your calendar wirelesly or via cable?
Also just as an FYI a BlackBerry device is set to reserve a large portion of the device memory for media files. As a result, email messages can be removed to free up space when the memory is low. You can reduce the preserved limit for media files by following these steps:
- On the BlackBerry smartphone Home screen, click Media.
- Select a media type (Music, Video, Ringtones, Pictures).
- Press the Menu key and select Options.
- Reduce the value set in the Device Memory Limit field. This field sets the maximum amount of memory available for all media files.
- Reduce the value set in the Reserved Pictures Memory field. This field sets the amount of memory reserved for picture files.
- Press the Menu key and select Save.
- Reduce the number of media files stored on your BlackBerry smartphone in order to meet the limit set in the Device Memory Limit field. For example
- Transfer the files to a media card. For instructions, see KB05478.
- Transfer the files to your computer using Media Manager in BlackBerry® Desktop Manager. For instructions, see KB05456.