transaction wraparound

Hi,

I am getting database shutdown issues as transaction wraparound limit hits 999999.

Here is the story...
We recently inherited a system in which a postgresql 8.1.18 server hosts 700+ databases and growing. Essentially it is horizontal partitioning per user, but on a single physical sever. Each database is on avg 250M. Vacuum Full Analyze takes 30 sec per database. The web interface performs 100,000’s transactions per request (99% read). We have up to 200 concurrent connections. We seem to reach the transaction id limits faster than we can vacuum.

Any suggestions on how to deal with this issue?? (without re-architecting if possible)

Autovacuum parameters...
vacuum_cost_delay = 10 # 0-1000 milliseconds
#vacuum_cost_page_hit = 1 # 0-10000 credits
#vacuum_cost_page_miss = 10 # 0-10000 credits
#vacuum_cost_page_dirty = 20 # 0-10000 credits
vacuum_cost_limit = 200 # 0-10000 credits
autovacuum = on # enable autovacuum subprocess?
autovacuum_naptime = 8642 # time between autovacuum runs, in secs
#autovacuum_vacuum_threshold = 1000 # min # of tuple updates before
# vacuum
#autovacuum_analyze_threshold = 500 # min # of tuple updates before
autovacuum_vacuum_scale_factor = 0.4 # fraction of rel size before
# vacuum
autovacuum_analyze_scale_factor = 0.2 # fraction of rel size before
autovacuum_vacuum_cost_delay = -1 # default vacuum cost delay for
# autovac, -1 means use
# vacuum_cost_delay
autovacuum_vacuum_cost_limit = -1 # default vacuum cost limit for
# autovac, -1 means use
# vacuum_cost_limit

Thank you,
Tom