why so many duplicate url's purged?

Enclosed is a section from out squid cache log file for version
1.0.15.

When I looked at the size of our cache today it's size was much
smaller than I suspected. So I had a look at the cache log and found
a very large number of 'duplicate url's purged' and 'swapfile clashes
avoided'.

Normally there are no 'duplicate url's purged' and only a few
'swapfile clashes avoided'.

Has anyone any idea why this happened?

       \\|//
      -(@ @)-
===oOO==(_)==OOo===================================================
          ************ NEW TELEPHONE NUMBER ************
Gareth Blades | Tel: +44 (0)1329 443564 | Segensworth Road
gblades@as.neag.co.uk | Fax: +44 (0)1329 443423 | Titchfield
IT Engineer | WWW: www.neag.co.uk | Fareham, Hants
Assessment Services | | PO15 5RH, England
===================================================================

-------------- Enclosure number 1 ----------------
[11/Dec/1996:01:45:01 +0000] main.c:415: Starting Squid Cache version 1.0.15 for i586-unknown-linux...
[11/Dec/1996:01:45:01 +0000] main.c:418: With 256 file descriptors available
<SNIP>
[11/Dec/1996:01:45:11 +0000] store.c:1528: Finished rebuilding storage from disk image.
[11/Dec/1996:01:45:11 +0000] store.c:1529: 19753 Lines read from previous logfile.
[11/Dec/1996:01:45:11 +0000] store.c:1530: 5279 Objects loaded.
[11/Dec/1996:01:45:11 +0000] store.c:1531: 261 Objects expired.
[11/Dec/1996:01:45:11 +0000] store.c:1532: 7120 Duplicate URLs purged.
[11/Dec/1996:01:45:11 +0000] store.c:1533: 7092 Swapfile clashes avoided.
[11/Dec/1996:01:45:11 +0000] store.c:1534: Took 8 seconds ( 659.9 objects/sec).
[11/Dec/1996:01:45:11 +0000] store.c:1536: store_swap_size = 141398k
<SNIP>
[12/Dec/1996:01:05:07 +0000] main.c:265: Preparing for shutdown after 683 connections
[12/Dec/1996:01:05:07 +0000] main.c:267: Waiting 30 seconds for active connections to finish
<SNIP>
[12/Dec/1996:01:05:08 +0000] store.c:2831: Finished. Wrote 5255 lines.
<SNIP>
[12/Dec/1996:01:45:05 +0000] store.c:1528: Finished rebuilding storage from disk image.
[12/Dec/1996:01:45:05 +0000] store.c:1529: 5255 Lines read from previous logfile.
[12/Dec/1996:01:45:05 +0000] store.c:1530: 5152 Objects loaded.
[12/Dec/1996:01:45:05 +0000] store.c:1531: 103 Objects expired.
[12/Dec/1996:01:45:05 +0000] store.c:1532: 0 Duplicate URLs purged.
[12/Dec/1996:01:45:05 +0000] store.c:1533: 0 Swapfile clashes avoided.
[12/Dec/1996:01:45:05 +0000] store.c:1534: Took 2 seconds (2576.0 objects/sec).
[12/Dec/1996:01:45:05 +0000] store.c:1536: store_swap_size = 57820k
Received on Fri Dec 13 1996 - 06:17:29 MST