I inherited two databases under one DBM. One database run mainly OLTP and the other complex DSS queries. I have intra-parallel turn on, which slows down the OLTP db. Is there a way to turn off intra-parallel processing at the database level?

DB21085I Instance "db2inst1" uses "32" bits and DB2 code release "SQL08022"
with level identifier "03030106".
Informational tokens are "DB2 v8.1.0.89", "special_15295", "U800790_15295", and FixPak "9".
Product is installed at "/opt/IBM/db2/V8.1".

If you use one container per tablespace, then that may help prevent intra-parallel queries in many situations.

you set DBM parameters intra_parallel=YES and leave max_querydegree at the default value; you can set DATABASE parameter dft_degree to 1 Or leave it unset(defaults to 1). This will turn OFF parallel processing for the database.
Because you are using 32 bits, intra_parallel processing takes a segment of 256M memory leaving one with 1.5gig of memory for other database buffers. If you use intra_parallel processing go for 64bit db2.