Report database consuming entire disk

Hi,

On a Fortigate 600C, the 55GB log disk is being entirely consumed by the report database

log disk quota 0 MB
        disk log:            0            0
     dlp archive:            0            0
          report:            0        56104
      quarantine:            0            0
     ips archive:            0            0

Rebuilding the database using "execute report recreate-db" does not seem to have any effect.

The local reporting isn't required so can be removed completely, how can this data be deleted to recover the disk space? It is causing problems for wan optimisation.

Thanks,