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Old 1st September 2009, 06:22
tem tem is offline
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Question how to calculate cache size for LDAP DB

Hi All,
I’m tuning my LDAP DB (BDB type).
I’m reading at http://www.openldap.org/doc/admin24/...y%20DB%20Cache

#(Number of hash buckets + number of overflow pages + number of duplicate pages) * page size / 2
#The objectClass index for my example database is 5.9MB and uses 3 hash buckets and 656 duplicate pages. So:
# ( 3 + 656 ) * 4KB / 2 =~ 1.3MB.
#With only this index enabled, I'd figure at least a 4MB cache for this backend. (Of course you're using a single cache shared among all of the database files, so the cache pages will most likely #get used for something other than what you accounted for, but this gives you a fighting chance.)”
I understand that: with each index ( in this case only objectclass is indexed), we must calculate their cache size individually and sum every them. (1)
- I can specify “Number of hash buckets” & “Cache Size “ (2)by command
Shell> db_stat-4.4 -m | head -n 25
32771 Number of hash buckets used for page location
Pool file: <index>.bdb
<number> page size
- I can specify “Number of overflow pages” & “Number of duplicate pages” by command
Shell> db_stat-4.4 -d *.bdb (3)
0 Number of tree duplicate page
0 Number of tree overflow pages
(1) Did I understand right?
(2) Which page size will we use, some of index file use 4K page size, others use 16K page size?
(3) Do must I run for each index or *.bdb is still ok?

Could anyone help me? This chapter is not clearly huh?

Thank for reading
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