Jason and all,
Attila words are wise, but there is more.
From your email, I'm not certain if you are talking about one data base
or a collection of data bases.
It's good that you have an image copy (copies) and apparently the DBDs,
but there is more to it.
Do you know if your data bases have compressed segments?
Do you know the format of the image copy? There are many.
Do you know if there are logical relationships? Even with a single data
base, they can be recursive.
Do you know if any of the data bases are Fast Path?
Do you know if any of the data bases are PDF (BMC Software product)?
These and other issues mentioned can make what you are trying to
accomplish very complex especially without the right tools and skills.
Tom Harper
Phoenix Software International
On 5/21/2024 3:57 AM, Attila Fogarasi wrote:
Jason, your applications will be in for a big surprise if you follow this
conversion path.
For example, PIC 9(4) COMP is a binary numeric field which is BIG ENDIAN on
mainframe, most (but not all) LUW and cloud systems are LITTLE ENDIAN. So
you need to convert these fields, otherwise the numbers change
dramatically. There are many other application specific data types that
were possible -- you will have to examine all of the application programs
for their field definitions and usage in order to determine the conversion
rules needed to preserve application data.
For example, on your question about multiple copy books this means that
different parts of the application have a different schema view of the
database. You will have to understand the significance of this, for
example a very common past technique is to have flag bytes which indicate
which of the many copy books to use for mapping the specific IMS segment.
So the same data, from the IMS database viewpoint, can look very different
for the application. You will need to capture this logic in the conversion
process, otherwise the data will be partly corrupted.
Your questions indicate you are focusing on the easy part of the problem,
and have not looked at the hard part at all. If you can't convert the
data, then what happens to the applications? Is there a regulatory
requirement? It may be cheaper to keep the old IMS system running as a
data reference site and run ad hoc application exports using custom logic.
Of course that requires understanding the applications in some depth.
On Tue, May 21, 2024 at 7:08 PM Jason Cai <ibmm...@foxmail.com> wrote:
Dear Micael and all
Thank you very much for your response and the valuable information
provided. Over the past few days, I discussed the DBD definitions with our
IMS DBA, and we have a similar setup
where “The only fields that are required to be defined in a DBD are the
keys, indexed fields, and any other fields that the application wants to be
able to reference in Segment Search Arguments (SSAs).
In the IMS system I work on, 99% of the segment fields are not defined in
the DBD.”
We are considering moving away from the mainframe, and our historical
data is preserved on tape in IMS unload format and IMS IC.
Initially, we wanted to convert the IMS database to a DB2 and then into a
MySQL database to facilitate the migration of backup data from the
mainframe to linux.
Now, we are only planning to transcode the IMS unload files to make them
readable on the Linux platform.
We have all the necessary copybooks and are currently looking to convert
these IMS unload files from EBCDIC to UTF-8 encoding.
Here are a few questions regarding the conversion process:
1.For fields in the copybook defined as PIC A, PIC X, and PIC 9, these
require conversion, but for numeric fields like PIC 9(4) COMP-1, no
conversion is needed, correct?
2 How do we handle the conversion if the database has multiple copybooks?
3 What is the process for converting variable-length fields?
4 If we choose not to convert anything, are there any tools available on
Linux that can read these IMS unload files in EBCDIC encoding?
5.Does the IMS unload file include information about segments, and how are
they encoded?
Furthermore, we do not have access to Broadcom IMS tools or File
Manager.
Could you please inform me if IBM has any utilities that can create the
unload format file from an image copy input?
Any advice or suggestions you can provide would be greatly appreciated.
Best regards，
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