When you need to sequentially read a large table, you can
improve performance by using a parallel serial scan.
The ALLBASE/SQL optimizer uses a parallel serial scan when it is
able to prefetch pages from multiple disk drives in parallel.
A parallel serial scan is useful only for large tables that must
be read sequentially. It is not beneficial for small tables
or for tables that are accessed only by an index.
To take advantage of a parallel serial scan, the following conditions
must be met:
The DBEFileset containing the table must contain multiple DBEFiles.
The DBEFiles containing the table must be placed on separate
disk drives.
You can specify the disk drive with
the DEVICE clause of the CREATE DBEFILE statement.
If the DBEFile has already been created, you can use
the SQLUtil MOVEFILE command.
The DBEFiles cannot be
raw because the file system's prefetching must not be bypassed.
The DBEFiles must not contain pages from other tables or index
pages from the same table. Put other tables in different DBEFilesets.
Use separate INDEX and TABLE DBEfiles for the index and data
pages of the table.
