Best Practices for SAP BI using DB2 9 for z/OS - IBM Redbooks

Column Local
or join
CALMONTH Local BETWEEN Yes 5 Optional
The mandatory columns to support the join and the majority of the filtering are
the join predicates (if you recall, the local predicates filtered from 7 million to 1
million rows, but the join predicates filtered down to 8 rows). All local predicates,
therefore, are listed as optional.
CALMONTH is a strong candidate to be the partitioning column. This provides
many benefits for maintenance (REORG, backup, and so on, only required on
the most recent partitions, as older partitions do not change over time), and also
for exploitation by other queries without the column required in the index (with
DB2 table controlled partitioning).
CURTYPE has only two possible values, which makes this a relatively poor index
choice, but it could be a good partitioning candidate (preceding CALMONTH) to
add greater granularity of each partition if required. CURTYPE should only be
added to the index, or as a partitioning column, if an equals predicate always
exists in queries against the DSO.
ACCT_ASGN is also not a strong filtering column, and has the disadvantage of
an IN list rather than equal predicate coded against it. IN list predicates are not
preferred for index matching for lower cluster ratio indexes (less than 80%)
because list prefetch cannot be exploited with matching IN list access. Therefore,
this column may not be a good choice for indexing unless the column is always
existing in queries and the column belongs to a high cluster ratio index.
The index recommendations for table /BIC/AZOSASALE00 are shown in
Table 10-3.
Table 10-3 Index recommendation
Column Reason
Operator Partition
candidate
222 Best Practices for SAP BI using DB2 9 for z/OS
Index
column
sequence
Mandatory/optional
CURTYPE Only if local predicate always exists in queries, and column is not
chosen as a partitioning column
ACCT_ASGN Only if local predicate always exists in queries, and index provides
good clustering
/BIC/ZMATLPLNT To support join filtering
PLANT To support join filtering
CALMONTH Only if not chosen as partitioning column