TurboIMAGE/XL Database Management System Reference Manual MPE/iX V6.5 (30391-90011)

Chapter 11 493
B-Tree Indices
Overview of B-Tree Indices
Key Points
These are the key points of TurboIMAGE/XL B-Tree indices:
• You can create a B-Tree index only on the key item of the master data set.
• Although you can create a B-Tree index only for the key item of a master data set, you
can still perform a B-Tree search using the search items of all of its corresponding
detail sets as well. A master data set is perceived as having an explicit B-Tree index
and each of its corresponding detail data sets is perceived as having an implicit
B-Tree index.
• You may create B-Tree indices for zero, one, or more data sets.
• DBSCHEMA has a new option, INDEXED, for the SET specification.
• DBUTIL has new commands and options.
a. New ADDINDEX, DROPINDEX, and REBUILDINDEX commands (to be used for one,
more than one, or all masters)
b. The SET command has a new BTREEMODE1 option to set DBFIND mode 1 access
ON or OFF for a B-Tree wildcard search for X and U types. The default is OFF. The
ON setting allows you to use B-Tree indices for generic search without making
application changes.
c. The SET command allows you to define your own database-wide wildcard character.
d. CREATE, ERASE, PURGE, SECURE, RELEASE, and SHOW commands include
B-Tree index files in their operation.
e. The MOVE command does not allow moving the index file.
• DBCONTROL has these modes pertaining to B-Tree indices:
13 is for B-Tree index file control. That is, to ADD, DROP, REBUILD,
ATTACH, or DETACH a B-Tree index file.
14 is used to set database-wide BTREEMODE1 and wildcard character.
15 sets BTREEMODE1 ON for the current DBOPEN (base parameter), and
optionally allows the wildcard character to be set for the current
DBOPEN.
16 sets BTREEMODE1 OFF for the current DBOPEN (base parameter).
• DBINFO has these modes pertaining to B-Tree indices:
209 informs whether or not a B-Tree index exists for a master.
113 gives BTREEMODE1 setting and the wildcard character for the
database as well as current DBOPEN.
• DBPUT or DBDELETE to an indexed master triggers a similar operation to indexed
master's B-Tree index file. (DBUPDATE to a master data set to modify a key item, despite
CIPUDATE setting, is not allowed.)
• DBFIND has these features pertaining to B-Tree indices:
a. Can be used for details as well as masters to specify B-Tree index searches.