CICS availability solution

subratarec · Posted: Thu Dec 20, 2018 9:28 am

Hi,

Currently in my organization we are working on a project whose main objective is given below...

Problem:
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•Application configurations cannot take advantage of Mainframe HA capabilities
•Application platforms (e.g. MSO) go “dark” during scheduled maintenance windows and system outages
•Capacity related outages due to application “hard coded” to specific LPARs

Objective:
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•Eliminate application availability due to single LPAR capacity issues or hardware failure
•Dynamic workload routing to the CEC, LPAR, CICS region or DB2 subsystem based on resource availability

Now to implement this feature we got to do bunch of different work. Among all types of work we are currently concentration of our TSQs and TDQs.

Now for TSQ the solution given to us that we need to create new TSQMODEL and while using the TSQ the load will be distributed among all the regions (if I understood correctly)

Now for TDQs we have much bigger issue. CICS team is saying there is no concept of TDQMODEL (like what we have in TSQ). We have more than 200 programs which are using TDQs (mostly for ATI purpose). So mean many programs and many different TDQs. Now they are saying we can not use TDQs and we are in big trouble. Still not sure what we can replace these TDQs with and we need to have the ATI facility also. Don't know how to go about it. Cause the solution we are trying should leave us very minimal change in our existing program (as we have many programs).

So does anyone faced this kind of issue and if yes, then what should be correct approach where the program changes would be minimal?

We were thinking MQ. One message to MQ and then trigger the corresponding transaction or what about 'Extra Partition TDQ'? Is it possible to share - Extra Partition TDQs amoung different LPAR.

Need your suggestion!! The above is what I understood if there is anything wrong in terminology please let me know I will recheck our documentation.

Thanks

Rohit Umarjikar · Posted: Thu Dec 27, 2018 12:33 am

subratarec · Posted: Thu Dec 27, 2018 2:02 pm

Hi Rohit,

Thanks for your reply. Yes as you have mentioned a pretty big CICS team is working on it. We already have listed CICS affinity commands and with that which all programs are having Low/Medium/High complexity of those affinity commands.

As I mentioned above we have found ways to deal with our TSQs and we already have started working on that (solution is - creating TSMODEL against specific PREFIX under a single GROUP).

In TSQ solution we don't have do much changes in our existing programs (cause we are utilizing current TSQs and rest of the thing will be handled internally by TSMODEL setup)

But the same kind of solution I couldn't find for TDQs. I searched and found that unlike TSQ, TDQ we can't create any such model and thats the reason we have make code changes to eliminate TDQs. Now TDQs we have used extensively because of data passing from one CICS programs to another with ATI facility. Now my query is that I am thinking if we can replace all TDQs with MQs (which will be used internally) and is that correct approach or is there any other way where we can share TDQs also like TSQ?

Note - As we are the owner of our CICS program so it seems we only have to think what is best or easy for us as far as the solution is concerned and have to give the plan to the main CICS ADMIN/SYSTEM PROGRAMMER team. They will review and may come back to us.

I am current checking the link you have provided.

Thanks

Rohit Umarjikar · Posted: Thu Dec 27, 2018 10:40 pm

subratarec · Posted: Mon Dec 31, 2018 10:18 pm

Rohit Umarjikar · Posted: Mon Dec 31, 2018 10:37 pm

May be it’s time you ask why TDQs needs to be removed. Second you could use DB2 or MQs but you could also take advantage of TSQs and CICS START to trigger transactions based on certain depth to replace ATIs.

subratarec · Posted: Wed Jan 02, 2019 11:56 pm

Hi Rohit,

Thanks! for your reply on this. I had thought of using MQ but implementing will be too much overhead so as you have mentioned above I planned for TSQ with CICS START to implement ATI logic. Now I shared my plan and below is what I got in reply..

Rohit Umarjikar · Posted: Thu Jan 03, 2019 1:10 am

I am sure they don’t have enough knowledge of other possibilities of achieving the objectives they have in hand.
1.Ask them to have two GORs defined for two regions.
2. Define two ENQ models one for local region and other one would be shared model for all other regions paired with local one.
3.Ask then to explore more on CICSplex SM, which is suggested already.
4.if you handle shared enqs across cics regions then no way you can interrupt any other task in any region for the same transaction.
5.You can issue a Start and let CICSplex SM decides in which region it needs to be executed based on the health of each region. You don’t need to control that programmatically.
6.MQs add more work of creating and managing them and hence lots of MQI Calls so if it can be avoided then why not?
7.Enq and deq won’t slowdown anything, we have them in all our programs.
8. You have to make TSQ name unique, task# or/and region name, terminal id should be part of TSQ name. So this way you won’t be able to delete someone else’s data and that’s the basic of naming TSQs.
9. Moreover, I am curious how do they plan to trigger a Transaction in a perticular region for high availability using MQs and without CICSPlex?

subratarec · Posted: Thu Jan 03, 2019 10:48 am

Hi Rohit,

Thanks! again for your valuable comments on the topic. Yes, I am going through what all points you have written above and I will try to present those points to the management. At the same time, I guess I have to gain more knowledge on CICSPlex SM product cause if they come back to me with more complicated questions then I should be able to at least address that.

From the beginning, I told them I will keep TSQ names unique (4 char trans id + EIBTRMID) then not sure how come other transaction (or same instances of the same transaction) will be able to delete the data? But as you have mentioned above deletion is not possible.

But one point I didn't get and that is GOR. I am not sure what is this GOR. Could you please let me know what 'GOR' stands for? I know AOR,TOR,FOR etc. but no idea on GOR.

Thanks

Rohit Umarjikar · Posted: Thu Jan 03, 2019 11:44 am

Sure, present them these questions and see what they have to say about it.
GOR - Gateway Owning Region. This option goes hand in hand with CICSPlex.

subratarec · Posted: Fri Jan 04, 2019 10:28 am

Hi Rohit,

I wrote an email to the HA contact person and tried to explain what you have given above. Now that person doesn't have end to end knowledge on HA setup and it's infrastructure so it seems he will pass my info to the main HA technical team and we may have meeting with them.

NOTE - It seems they are implementing CICSPlex SM product only.

Thanks

Rohit Umarjikar · Posted: Fri Jan 04, 2019 10:30 am

Very well. It’s very interesting concept to work on and specially fun and challenging when performing volume tests.

You need lot of testing efforts to test and compare Monoplex vs CICSplex region results to make sure they are 100% accurate.

subratarec · Posted: Mon Jan 07, 2019 10:40 am

Hi Rohit,

Thanks! for all the help and information. Yes, I am very new this kind of assignments. Maybe this would be a good learning for me but again because I work for an Investment Bank's Wealth Management division we have something called ZDAP - Zero Developer Access Policy and with this policy they have removed all of our main access from QA/PROD region (CICS or DB2 etc.) so sometimes it is very tough for us to learn more about setup related things.

Current a dedicated team is working on VSAM changes (enabling RLS option) and soon we will have to start working on this CICS thing..

I may have to come back again to you if I need any guidance on the same and hope you will assist me they way you did this time.

Thanks

Rohit Umarjikar · Posted: Mon Jan 07, 2019 7:40 pm

You are welcome 🙏.

subratarec · Posted: Tue May 28, 2019 10:32 am

Again I am replying to this thread. Actually after few months of pause we had meeting with our CICS Integration/System people. I tried to present my thought on how we can have TDQs and no need to replace TDQ with MQ.

But it seems they are pre determined that they will move away from TDQ and will adopt MQs in place of TDQs. In the end it is basically they are passing the bucket to us (application programmers) cause to replace all TDQs to MQs we need to make significant code change.

Now I have another query for CICS HA. That meeting a topic surfaced and that is let's say we have initiated a transaction in one region (lets say by CICS START) and during it's run in that region suddenly because some unavoidable issue region goes down. Then in that scenario what happens? I mean how we can make sure that the transaction then can automatically be routed to another region? Is it possible with this CICSPlex SM env?

May be it is possible and I am not aware of it. But wanted check with you. In that scenario will rollback happens for that transaction and it gets restart/routed automatically in another region so business process should not get affected?

Could you please your thought on the same?

Thanks

Rohit Umarjikar · Posted: Wed May 29, 2019 1:13 am

You are mixing couple of things together... let me try to them answer one by one.

1. If the transaction fails in Monoplex CICS then DTB happens and logs are created and in this case rollback happens and messages remains in MQ. Now based on TriggerType the transaction is self started after certain specified interval or manually by MQSET if type DEPTH is chosen. This is a usual way of working without CICSplex SM.

2. Now with CICSPlex SM paired regions, say rgn1 and rgn2 are paired together for HA. Now certainly transaction sequencing is done thru ENQ and DEQs and there will be now two ENQ models that needs to be defined. Local and Shared ENQ models. In such enabled environments when a transaction is triggered it first comes to GOR (Gateway Owing Region(s)) where the two tasks are created at the same time say tsk1 and tsk2 into rgn1 and rgn2 respectively and based on CICSPlex SM decision either one region takes the priority and executes it and other task (tsk2) goes on wait in shared ENQ as well as Local ENQ. So say rgn1 has got a problem and it crashed so the hold is released and DTB and that's where tsk2 in rgn2 takes the control and starts executing by acquiring LOCAL and SAHRED ENQ. Now there could be more than 2 regions paired and same logic flows thru rest of the regions.

I hope this helps.

subratarec · Posted: Thu May 30, 2019 11:55 pm

Hi Rohit,

Thanks!! a ton for your time and reply. I am going through what you have explained above and the link you have given. As usual for any query I may bother you a bit

Thanks

Rohit Umarjikar · Posted: Fri May 31, 2019 12:17 am

No Problem, You're Welcome!!.