Txn_checkpoint and Malloc

[David Brown <daveb21@gmail.com>]

I'm wondering if anyone can shed any light on the following issue i'm
having with OpenLDAP 2.2.20 (BDB 4.3.21 - i know that 4.2.52 is
recommended but haven't had a chance to revert back to that release
yet) on RHEL3.

There are a lot of adds / deletes / modifies happening to this master
server and there are a fair few messages of the following in my ldap
logfile (loglevel 256). The 2 syncrepl slaves we have as consumer's of
this server do not show the same behaviour.

Apr  6 07:35:05 decs-ldap1 slapd[24033]: bdb(dc=sa,dc=edu,dc=au):
malloc: Cannot allocate memory: 3145764
Apr  6 07:35:05 decs-ldap1 slapd[24033]: bdb(dc=sa,dc=edu,dc=au):
txn_checkpoint: failed to flush the buffer cache Cannot allocate
memory

Haven't really been able to find much in the way of what might be
causing this or how to fix it.

The database LDIF is about 185Mb. I attach below the DB_CONFIG and
relevant portions of slapd.conf

DB_CONFIG
set_lg_max 104857600
set_lg_regionmax 262144
set_lg_bsize 10485760 
set_lg_dir /var/lib/ldap
set_flags DB_LOG_AUTOREMOVE
set_lk_max_locks 2000
set_lk_max_objects 2000

# ONLY FOR SLAPADDS
#set_flags DB_TXN_NOSYNC

set_cachesize   2       0       1

slapd.conf
database        bdb
checkpoint      1024 5
cachesize       100000
idlcachesize    100000

## Index Set
index   uid             eq
index   uidNumber       eq
index   gidNumber       eq
index   memberUid       eq
index   ou              eq
index   cn              pres,eq,sub
index   sn              pres,eq,sub
index   objectclass     pres,eq
index   member                  eq
index   mailAlternateAddress    eq
index   mailLifeLongAddress     eq
index   mailDefaultAddress      eq
index   mailForwardingAddress   eq
index   mailRoutingAddress      eq
index   mailHost                eq
index   mail                    eq
index   employeeNumber          eq
index   relayAllow              eq
index   relayDomain             eq
index   accountStatus           eq
index   accessibility           eq                       
index   schoolURL               eq        
index   listOwner               eq 
index   validStudentDateTime    eq
index   fqSchoolName            eq
index   ipRange                 eq
index   entryUUID               eq
index   default                 sub

I have realised that the cachesize and idlcachesize values aren't
optimal and i've been experimenting with different values but haven't
settled on the optimal value yet.

If anyone can shed any light on this one or give any suggestions that
would be great.

Thanks muchly,
_____________________
David Brown