Doing a binary search (SEARCH ALL)
If you use SEARCH ALL to do a binary
search, you do not need to set the index before you begin. The index
is always the one that is associated with the first index-name in
the OCCURS clause. The index varies during execution
to maximize the search efficiency.
About this task
To use the SEARCH ALL statement to search a table, the table must specify the ASCENDING or DESCENDING
KEY phrases of the OCCURS clause, or both,
and must already be ordered on the key or keys that are specified
in the ASCENDING and DESCENDING
KEY phrases. You can use a format 2 SORT statement
to order the table according to its defined keys, thereby making the
table searchable by the SEARCH ALL statement. Note
that SEARCH ALL will return unpredictable results
if the table has not been ordered according to the keys.
In the WHEN phrase
of the SEARCH ALL statement, you can test any key
that is named in the ASCENDING or DESCENDING
KEY phrases for the table, but you must test all preceding
keys, if any. The test must be an equal-to condition, and the WHEN phrase must specify either a key
(subscripted by the first index-name associated with the table) or
a condition-name that is associated with the key. The WHEN condition
can be a compound condition that is formed from simple conditions
that use AND as the only logical connective.
Each key and its object of comparison must be compatible according to the rules for comparison of data items. Note though that if a key is compared to a national literal or identifier, the key must be a national data item.
SEARCH statement (Enterprise COBOL for z/OS® Language Reference)
General relation conditions (Enterprise COBOL for z/OS Language Reference)