IMS DB checkpoint/restart



IBM's hierarchical database management system with a Database Manager (IMS DB) and a Transaction Manager(IMS DC)

IMS DB checkpoint/restart

Postby Abhi Shrivastava » Fri Jan 07, 2011 3:15 pm

Hi,

I want to know what may be the possible hazards of not coding checkpoint/restart in an IMS program? Can it lead to IMS region itself coming down. if yes, in what scenarios?

Thanks
Abhi
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Re: IMS DB checkpoint/restart

Postby dick scherrer » Sat Jan 08, 2011 8:42 am

Hello and welcome to the forum,

Many organizations no longer want developers to implement checkpoint/restart. . .

Suggest you speak with seniors or managers of your system and ask what is the current method. Whatever is standard, you should follow.
Hope this helps,
d.sch.
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Re: IMS DB checkpoint/restart

Postby Abhi Shrivastava » Sat Jan 08, 2011 10:03 pm

Hi Dick

Thanks for your reply. But I did exactly the same. I consulted my senior for the same.

I will brief you exactly what happened.

Actually I am a Mainframe DBA, predominantly on DB2. But new to IMS.

We are needed to write a COBOL IMS prgram that just issues the GU calls. So we thought we will not code for checkpoint/restart, as it is just GU call that will be issued by the program. But when our manager reviewed the program, he said that we should code for checkpint/restart also because as per his experience(although he does not remember what was the actual issue that time), once a programmer coded a COBOL program without checkpoint/restart logic, and it led to IMS region itself coming down.

So, I out of curiousity want to know what may be lead to such IMS region failure.

Could you please shed some light on this?

Thanks!
Abhi
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Re: IMS DB checkpoint/restart

Postby dick scherrer » Sun Jan 09, 2011 12:51 am

Hello,

I do not recall the lack of a checkpoint causing any database (not just IMS) to "come down". It may be that there were "too many" uncommitted updates in process but on the systems i've worked on, the problem task is terminated or there is a "forced checkpoint".

It may have been that this happened on some database implementation(s) in the past . . .

Suggest you work with your dba and run a controlled test in a test environment of a program that issues millions of add/update/delete transactions with no checkpoint and see what actually happens on your system. I would expect a "bad" return code from the database, not a shutdown of the database system. . .
Hope this helps,
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Re: IMS DB checkpoint/restart

Postby Abhi Shrivastava » Mon Jan 10, 2011 9:29 am

Thanks Dick!

Actually I am the only DBA here...

Is there a possibility that ...

if our program is running and abending again and again..this lead to lots of uncommited data lying in buffer space, causing important ims region controller program lack of space to run...that's why ims region crashing as it gets no space to run it's own programs.

I learned one more thing..a PSB will be stopped after 3 restart of a program..can this cause region crash?

Regards,
Abhi
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