File Management - IBM

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The to-file must contain the correct result format description. The from-file data
must be in the same corresponding position as the to-file data. Otherwise, output
mapping errors or unpredictable results may occur. Date, time, and timestamp data
must be in the external form of the to-file field specification. Numeric data types in
the to-file must be large enough to contain the expected data. For example, decimal
data types in the to-file must be created using the maximum possible precision for
the byte length of the field to avoid the loss of any digits. Because there are no
CCSID conversions, the to-file fields should be created with the expected CCSIDs.
Errors in converting system/370 floating point and null fields
Any conversion errors will cause CPF2958 messages to be issued for up to 10
records with errors. A CPF2959 message will be issued after the copy operation;
this message indicates the number of records that caused an error if more than 10
records caused conversion errors.
If there are no floating point fields in the to-file and *CVTFLOAT is specified, no
error messages are issued. However, no floating point conversion is done. If you
have not specified any null-capable fields in the to-file and *NULLFLAGS, no error
messages are issued. However, the from-file data is assumed to have no null bytes
(or flags). When you use *CVTFLOAT and *NULLFLAGS, the CPYF command
expects the from-file data to be defined by the to-file format.
You should use the *CVTFLOAT and *NULLFLAGS values only for files that
require conversion of the System/370 hexadecimal floating point fields or
conversion with null flags. Using these values for other files may cause
unpredictable results including possible data corruption and output errors.
System/370 floating point fields must be converted only once. If the fields are
converted more than once, multiple conversions occur, and the data will be
damaged.
This CPYF function is compatible with the data that is placed on tape by the DB2
unload function (DSNTIAUL). You must manually create the result tables or files
with SQL or DDS on the AS/400 system before you can run the CPYF function to
convert the data; use the formats produced by the DSNTIAUL function to do this.
Conversion rules for copying files
Table 15 on page 120 shows the field conversions that are allowed between
mapped fields in the from-file and to-file record formats. If fields with the same
name have incompatible attributes between the from-file and to-file formats, you
can only use FMTOPT(*NOCHK) to perform the copy. An X indicates that the
conversion is valid, and a blank indicates a field mapping that is not valid.
When mapping character fields, the field being copied is truncated on the right if it
is longer than the field into which the copy is made. For example, a character field
of length 10 is copied into a character field of length 6; ABCDEFGHIJ becomes
ABCDEF. If the field that is being copied is shorter than the field into which it is
copied, the field is padded on the right with blanks. For example, a character field
of length 10 is copied into a character field of length 12; ABCDEFGHIJ becomes
ABCDEFGHIJxx (x = blank).
When you are mapping numeric fields, and the field being copied is longer than
the field into which the copy is made, the field being copied is truncated on the
left and right of the decimal point. For example, a zoned decimal field of length 9
Chapter 4. Copying files 119