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DDM Files
The DDM file provides the information needed for a local system to locate a remote
system and to access the data in the source file. For more information about using
DDM and creating DDM files, refer to the
Distributed Data Management
manual.
Using Pre-V3R1 DDM Files
If you are using a pre-Version 3 Release 1.0 DDM file, the key comparison is not
| done at the Data Management level during a READE or READPE operation, EQ
| indicator for SETLL, or during sequential-within-limits processing by a record
| address file. The READE or READPE operation, EQ indicator for SETLL, or during
| sequential-within-limits processing by a record address file, will instead compare the
keys using the *HEX collating sequence.
This may give different results than expected when DDS features are used that
cause more than one search argument to match a given key in the file. For
example, if ABSVAL is used on a numeric key, both -1 and 1 would succeed as
search arguments for a key in the file with a value of 1. Using the hexadecimal
collating sequence, a search argument of -1 will not succeed for an actual key of 1.
Some of the DDS features that cause the key comparison to differ are:
ALTSEQ specified for the file
ABSVAL, ZONE, UNSIGNED, or DIGIT keywords on key fields
Variable length, Date, Time, or Timestamp key fields
The SRTSEQ for the file is not *HEX
ALWNULL(*USRCTL) was specified on the creation command and a key in the
record or the search argument has a null value (this applies only to externally
described files)
In addition, if the sign of a numeric field is different from the system preferred sign,
the key comparison will also differ.
The first time that the key comparison is not done at the Data Management level on
| a pre-V3R1 DDM file during the READE or READPE operation, EQ indicator for
| SETLL, or during sequential-within-limits processing by a record address file, an
informational message (RNI2002) will be issued.
Note: The performance of I/O operations that have the possibility of not finding a
record (SETLL, CHAIN, SETGT, READE, READPE), will be slower than the
pre-Version 3 Release 1.0 equivalent.
Chapter 16. Accessing Database Files 313