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the way to calculate the cache size.

Hi All,

                I’m tuning my LDAP DB (BDB type).

                I’m reading at http://www.openldap.org/doc/admin24/tuning.html#Berkeley%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