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DETERMINE; (DT) Commands
Handling of Duplicate Keys in MCP based LINC Systems
For an MCP based LINC System, the order in which records with duplicate key values are
retrieved depends upon the setting of the Duplicates First/Last Profile DASDL option, as
shown in the following table.
Duplicates DT Command Order of Duplicates
FIRST FROM Reverse order to that of entry
FIRST BACK Order of entry
LAST FROM Order of entry
LAST BACK Reverse order to that of entry
blank FROM/BACK Physical order of records in database (note that
this may change during a reorganization)
A database reorganize or garbage collect may alter the order of Duplicates First/Last
entries. For further details, see your Data and Structure Definition Language (DASDL)
Programming Reference Manual.
DETERMINE; Commands in ORACLE LINC Systems
The following issues can arise with UNIX ORACLE LINC Systems:
$ DETERMINE; BACK and DETERMINE; LAST command performance
ORACLE has no direct means of reading a Profile in reverse order. When executing
these commands, ORACLE may read and sort the entire Profile (table) to obtain the
required records.
$ Inappropriate ORACLE Index Selection
On occasion, ORACLE may select the wrong index (Profile) where the Indexes have
identical keys but in a different order. This can have performance implications for your
LINC System.
These issues and suggested solutions are described in your UNIX LINC Administration
and Operations Guide.
DETERMINE; Commands Over Multiple Logic Lines
DETERMINE; commands can be written over multiple lines, provided that line breaks
occur within the parentheses, and a line does not commence with a right parenthesis.
In DETERMINE; GROUP commands, the first line may break before any data item within
any of the parentheses sets.
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