Special considerations apply to the following cases in the IMS™ BMP or z/OS® batch environments:
- serial files implemented as GSAM (generalized sequential access
method) files
- IMS message queues
In either of these cases, be aware of the following considerations:
- An add statement for a serial record
that is associated with a sequential (non-VSAM) file adds data to
the beginning of the file and loses all previous data, unless the
file is allocated using DISP=MOD in the JCL for the batch job. Until
the file is closed, subsequent add statements
place data following the previously added data.
- A single program cannot include a combination of add and get
next statements for the same GSAM file.
- An add statement for a serial record
associated with a GSAM file results in an ISRT call to the GSAM database.
The program starts adding the records at the beginning of the file
unless the file is allocated using DISP=MOD in the JCL for the batch
job. Until the file is closed, subsequent add statements
place data following the previously added data.
- If you add a variable-length serial record to a file associated
with GSAM and the record length is longer than the physical file,
DL/I returns a blank status code. Data is truncated, but no message
is issued because the situation cannot be detected.