A lot of our sessions were curiously large, sometimes approaching 2 megabytes per session. Because sessions are read and rewritten on every request that uses the session, this generates a fair bit of traffic. After decoding the stored session information, I walked the session looking for the culprit. cal_courses_shown appeared to be the largest offender, so I wrote a test script which evaluated the top 10 sessions at the time. The number in the parentheses is the "before" size. The number after "Now:" is the "after" size. The only change that I made to the session was to run the following line of code:

unset($_SESSION['SESSION']->cal_courses_shown);

My results follow:

_Start_

Session #1 (1282077)
Now: 5251 (99.59% savings)

Session #2 (1113736)
Now: 5449 (99.51% savings)

Session #3 (870381)
Now: 5489 (99.37% savings)

Session #4 (487920)
Now: 5658 (98.84% savings)

Session #5 (451477)
Now: 5143 (98.86% savings)

Session #6 (440864)
Now: 5300 (98.80% savings)

Session #7 (255664)
Now: 5915 (97.69% savings)

Session #8 (255311)
Now: 5562 (97.82% savings)

Session #9 (255211)
Now: 5462 (97.86% savings)

Session #10 (255160)
Now: 5411 (97.88% savings)

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