MTS transactions

grad · Apr 25, 2000

I am new to MTS but I have developed COM objects in VB before.  I am using VB6. Scenario: If I have a functions withdraw(account, amount) and deposit(account, amount) the two functions can process transactions independently.  Within each function I connect, do work and then disconnect from the database. Question: can I do the following in the class/com object function transfer(account1, account2, amount)    withdraw(account1, amount)    deposit(account2, amount)    setcomplete/setabort and MTS will know that both transactions need to be committed or aborted as a unit thanks mark

Guest_imported · Apr 25, 2000

hi grad, The answer to your question is YES. MTS will take it as one unit. Backgrounders:- To be part fo a transaction a component running under MTS must be configured under one of the following categories. 1. Requires new Transaction 2. Requires Transaction 3. Supports Transaction. For case 1 whenever the component is instantiated a new transaction is started for it automatically by MTS. For case 2 whenever the component is instantiated there are 2 possibilities.     a. If the component A is instantiated from inside a method of another component B that is already in a transaction then component A becomes part of the transaction of component B.      b. If the above is not the case then a new transaction is automatically started by MTS. For case 3 if the component is instantiated from inside the method of another component that is already in a transaction then it becomes part of the transaction else no transaction is started for it. This is similar to case 2 with a change in option b. The component developer need not explicitly start a transaction. He only needs to configure it under MTS. What he needs to do however is to either commit or abort the transaction. Therefore all database operations become part of a transaction until setabort or setcomplete is called. Taking your case when the function transfer is called and provided the component is configured be transactable then until a setabort/setcomplete is called all database operations will be taken as one unit even though you may have opened and closed the connection many times in between. note:- it is always good practise to call setabort/setcomplete at the end of every method because apart from transaction these statements tell MTS that I have done with the object and you can deactivate it. this improves scalability. Does that clear your doubts????

grad · Apr 26, 2000

This helps a lot now for my second question!! On my client when I create an instance of the object, MTS starts a surrogate process.  Can I get the object context in my client and do the commits and aborts from the client or do I have to create another COM object under MTS to do this. i.e. This code will reside on the client... sub clientcode()    dim o1 as com.class        set o1 = createobject("com.class&quot

'creates the object   within MTS     i = o1.f1()     j = o1.f2()     if i = -1 or j = -1 then         getobjectconext().setabort     else        getobjectcontext().setcomplete    end if

juliaroberts · Apr 27, 2000

hi grad , first of all you cannot call "getobjectcontext" directly in your code even though this might not actually result in an error. in your VB code you should first implement Object control. eg:- implements ObjectControl this will have 3 events called:- 1.Objectcontrol_activate() 2.Objectcontrol_deactivate() 3. objectcontrol_canbepooled() inside objectcontrol_activate() you should write set ctx=getobjectcontext() the activate event will be fired automatically when the first method of the object is called which will initialize the object context. so as per your code:- if i = -1 or j = -1 then         getobjectconext().setabort  ---->>> error     else        getobjectcontext().setcomplete  --->>> error    end if the most likely error would be:- "with or set variable not set". So the answer to your question would be NO. You cannot do as you had suggested. Believe me I just tried it out. Please correct me if I am wrong bye

rookiejack · May 3, 2000

Hi Lovely julia has explained clearly about proper way of writing an MTS Component using an ObjectContext.  But, I feel she hasnt answered what grad asked, from what i understand... "Can I get the object context in my client and do the commits and aborts from the client or do I have to create another COM object under MTS to do this" To my knowledge, you cannot get the object context in the client.  You have to create another COM object.  If you are going to control transactions in the Client... the whole idea of MTS fails. Hope I answered you. Bye Jacky

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MTS transactions

grad

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grad

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