rbl-plus zone transfers

[Jorg B.]

Hello,

We are using Bind 9.2.4 on Slackware linux (kernel 2.4.29).
We are a subscriber of the rbl-plus.mail-abuse.org black list which is 
currently ~108Mb in size.
I have done some searching around and I know the the bind/rbl-plus issue 
is a known issue... but since all of the reports were over a year old I 
was wondering if anybody has found a solution to the problem.

Here is a description of the problem again:

When the server is doing a zone transfer of the rbl-plus.mail-abuse.org 
zone file the memory usage of bind is going up by a factor of 3 (which I 
understand is normal).
So, the 108Mb zone will take about 324Mb of ram. This means that 
including my other zone files named uses about 465Mb of RAM.
So far so good... The problem starts when named is doing another zone 
transfer of  the rbl-plus zone... Now the mem usage of named reaches 
about 900Mb.
A few hours later when the next zone transfer takes place the mem usage 
of named keeps going up. I understand that bind reads the zone into 
memory during a zone transfer, writes it out to a file, replaces the old 
zone file and finally reloads the zone... but why isn't named freeing up 
the *temp* memory after the zone is written to disk ?
My dedicated RBL DNS server currently has 1GB of Ram and 1GB of  swap 
which is not enough to handle the rbl-plus zone.

Any feedback ?

Thanks
JB