User Guide

SAP AG November 2002
JOIN_SEARCH_LEVEL
The special database parameter [Page 80] JOIN_SEARCH_LEVEL determines the algorithm
for the join sequence search. The level specified here determines how many resources and
how much time the join sequence search takes.
• 9 (Join sequence search level 9): All possible join sequences are calculated.
• 4 (join sequence level 4): Various join sequences are calculated, depending on the query
structure (transformer algorithm).
• 1 (join sequence search level 1): The simplest algorithm is used for the join sequence
search (greedy algorithm).
• 0 (classified join sequence search level 0, level 0 is the default setting): The algorithm
that is used for the join sequence search depends on the number of tables that were
selected in join.
Joins with n number of tables, where n<=JOIN_MAXTAB_LEVEL9 [Page
82]: Level 9 of
the join sequence search is used.
Joins with n number of tables, where
JOIN_MAXTAB_LEVEL9<n<=JOIN_MAXTAB_LEVEL4 [Page 82]: Level 4 of the join
sequence search is used.
Joins with n number of tables, where JOIN_MAXTAB_LEVEL4<n: Level 1 of the join
sequence search is used.
JOIN_MAXTAB_LEVEL4 is set to 16.
JOIN_MAXTAB_LEVEL9 is set to 4.
JOIN_SEARCH_LEVEL is set to 0.
5 tables are used for a join.
Join sequence search level 4 (transformer algorithm) is used for this join because
the database parameter JOIN_MAXTAB_LEVEL9<5<=JOIN_MAXTAB_LEVEL4
is most appropriate.
KERNELDIAGSIZE
The special database parameter [Page 80] KERNELDIAGSIZE denotes the size of log file of
the kernel [Page
140] in KB.
KERNELVERSION
The general database parameter [Page 79] KERNELVERSION denotes which database
software version is being used.
LOG_BACKUP_TO_PIPE
The special database parameter [Page 80] LOG_BACKUP_TO_PIPE determines whether or
not a log backup [Page
142] is permitted (YES) or not permitted (NO) in pipes.
User Manual: SAP DB 83