By default, DB2 stores a container tag in the first extent of each DMS container, whether it is a file or a device. The container tag is the metadata for the container. (Before DB2 v8.1, the container tag was stored in a single page, so it required less space in the container.) It is recommended that you keep this variable set to OFF.

The DB2_USE_PAGE_CONTAINER_TAG variable is set using the db2set command.

$ db2set DB2_USE_PAGE_CONTAINER_TAG=OFF
$ db2stop ;
$ db2start

If you set this registry variable to ON when you use RAID devices for containers, I/O performance might degrade. Because for RAID devices you create table spaces with an extent size equal to or a multiple of the RAID stripe size, setting the DB2_USE_PAGE_CONTAINER_TAG to ON causes the extents not to line up with the RAID stripes. As a result, an I/O request might need to access more physical disks than would be optimal. Users are strongly advised against enabling this registry variable.