When creating a DMS table space with many containers, DB2 UDB automatically 

distributes the data across them in a round robin fashion, similar to the striping 

method available in disk arrays. To achieve the best possible performance, each 

table space container should be placed on a dedicated physical device. For 

parallel asynchronous writes and reads from multiple devices, the number of 

database page cleaners (

NUM_IO_CLEANERS

) and I/O servers (

NUM_IOSERVERS

) 

should be adjusted. The best values for these two parameters depends on the 

type of workload and available resources. You can start your configuration with 

the following values:

  NUM_IOSERVERS

 = Number of physical devices, but not less than three and no 

more than five times the number of CPUs. 

  NUM_IO_CLEANERS

 = Number of CPUs

Example 9 31 shows how to set the initial values of the parameters for two 

processor machines with six disks available to DB2.

Example 9 31   Updating IO related processes

db2 update db cfg for sample using NUM_IOSERVERS 6

db2 update db cfg for sample using NUM_IOCLEANERS 2

If there is a relatively small number of disks available, it can be difficult to keep 

logical logs, data, indexes, system temporary table spaces (more important for 

processing large queries in a warehousing environment), backup files, or the 

operating system paging file on separate physical devices. A compromise 

solution is to have one large file system striped by a disk array (RAID device) and 

create table spaces with only one container. The load balancing is shifted to 

hardware, and you do not have to worry about space utilization. If you want 

parallel I/O operations on a single container, the 

DB2_PARALLEL_IO

 registry 

variable should be set before starting the DB2 UDB engine.

By performing the following command, I/O parallelism will be enabled within a 

single container for all table spaces:

db2set DB2_PARALLEL_IO="*"

The following example enables parallel I/O only for two table spaces: 

DATASP1

and 

INDEXSP1

:

db2set DB2_PARALLEL_IO="DATASP1,INDEXSP1"

To check the current value for the parameter issue:

db2set DB2_PARALLEL_IO

300 

MySQL to DB2 UDB Conversion Guide