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Brief summary of previous episodes…


In the beginning it was Serialized V3 Update.

After examining the conception and technical background of delta extraction in Logistic Cockpit by using this method (Episode one: V3 Update, the ‘serializer’ ), we also examined all peculiar restrictions and problems related to its usage (LOGISTIC COCKPIT DELTA MECHANISM – Episode two: V3 Update, when some problems can occur…).

Since performance and data consistency are very critical issues for a datawarehouse and, from this point of view, the ‘serializer’ started showing its not so reliable face,

with advent of PI 2002.1 (or PI-A 2002.1) three new update methods came upand, as of PI 2003.1 (or PI-A 2003.1), these methods have been completely replaced Serialized V3 update method, that it’s no longer offered.


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Fig.1</b>: LBWE, Update Mode Selection Screen as PI.2002.1



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Fig.2</b>: LBWE, Update Mode Selection Screen as PI.2003.1


Now let’s meet our new guests and try to discover when it’s better to make use of one than another one!

h4. 1. New “direct delta” update method: when in R/3, life is not so berserk…


With this update mode, extraction data is transferred directly to the BW delta queues with each document posting.

As a consequence, each document posted with delta extraction is converted to exactly one LUW in the related BW delta queues.

Just to remember that ‘LUW’ stands for Logical Unit of Work and it can be considered as an inseparable sequence of database operations that ends with a database commit (or a roll-back if an error occurs).


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Fig.3</b>: Direct Delta update mechanism


Starting from the definition of this method we can see at once what are advantages and disadvantages resulting from direct delta usage.

BENEFITS AND…

As we can see from the picture above, there’s

no need to schedule a job at regular intervals(through LBWE “Job control”) in order to transfer the data to the BW delta queues; thus, additional monitoring of update data or extraction queue is not require.

Logically, restrictions and problems described in relation to the “Serialized V3 update” and its collective run do not apply to this method: by writing in the delta queue within the V1 update process, the

serialization of documents is ensured by using the enqueue conceptfor applications and, above all, extraction is independent of V2 update result.

…LIMITATIONS !

The number of LUWs per datasource in the BW delta queues increases significantly because different document changes are not summarized into one LUW in the BW delta queues (as was previously for V3 update).

Therefore this update method is

recommended only for customers with a low occurrence of documents(a maximum of 10000 document changes – creating, changing or deleting – between two delta extractions) for the relevant application.

Otherwise, a larger number of LUWs can cause dumps during extraction process and, anyway, V1 updatewould be too much heavily burdenedby this process.

Besides, note that

no documents can be posted during delta initialization procedurefrom the start of the recompilation run in R/3 (setup tables filling job) until all records have been successfully updated in BW: every document posted in the meantime is irrecoverably lost.

(Remember that stopping the posting of documents always applies to the entire client).

h4. 2. New “queued delta” update method: how to easily forget our old ‘serializer’…


With queued delta update mode,

the extraction data(for the relevant application) is written in an extraction queue (instead of in the update data as in V3)and can be transferred to the BW delta queues by an update collective run, as previously executed during the V3 update.

After activating this method, up to 10000 document delta/changes to one LUW are cumulated per datasource in the BW delta queues.


image

Fig.4</b>: Queued Delta update mechanism


BENEFITS, BUT…

When you need to perform a delta initialization in the OLTP, thanks to the logic of this method, the

document postings(relevant for the involved application) can be opened again</b> as soon as the execution of the recompilation run (or runs, if several and running in parallel) ends, that is when setup tables are filled, and a delta init request is posted in BW, because the system is able to collect new document data during the delta init uploading too (with a deeply felt recommendation: remember to avoid update collective run before all delta init requests have been successfully updated in your BW!).

By writing in the extraction queue within the V1 update process (that is more burdened than by using V3), the

serialization is ensured by using the enqueue concept, but collective run clearly performs better than the serialized V3and especially slowing-down due to documents posted in multiple languages does not apply in this method.

On the contrary of direct delta, this process is especially

recommended for customers with a high occurrence of documents(more than 10,000 document changes – creation, change or deletion – performed each day for the application in question.

In contrast to the V3 collective run (see OSS Note 409239 ‘Automatically trigger BW loads upon end of V3 updates’ in which this scenario is described), an

event handling is possible</b> here, because a definite end for the collective run is identifiable: in fact, when the collective run for an application ends, an event (&MCEX_nn, where nn is the number of the application) is automatically triggered and, thus, it can be used to start a subsequent job.

Besides, don’t omit that queued delta process extraction is

independent of success of the V2 update.

+…REMEMBER TO EMPTY THE QUEUE ! +

The ‘queued delta’ is a good friend, but some care is required to avoid any trouble.

First of all, if you want to take a look to the data of all extract structures queues in Logistic Cockpit, use transaction

LBWQor “Log queue overview”function in LBWE (but here you can see only the queues currently containing extraction data).

In the posting-free phase

before a new init runin OLTP, you should always execute (as with the old V3) the update collective run once to make sure to empty the extraction queue from any old delta records (especially if you are already using the extractor) that, otherwise, can cause serious inconsistencies in your data.

Then,

if you want to do some change(through LBWE or RSA6) to the extract structuresof an application (for which you selected this update method), you have to be absolutely sure that no data is in the extraction queue before executing these changes in the affected systems (and especially before importing these changes in production environment !).

To perform a check when the V3 update is already in use, you can run in the target system the RMCSBWCC check report.

The extraction queues should never contain any data immediately before to:

    R/3 or a plug-in upgrade

      1. import an

    R/3 or a plug-in support packages

    h4. 3. New “unserialized V3 update” update method: when a right delta sequence is not a requirement…


    With this update mode, that we can consider as the serializer’s brother, the extraction data continues to be written to the update tables using a V3 update module and then is read and processed by a collective update run (through LBWE).

    But, as the name of this method suggests, the V3 unserialized delta disowns the main characteristic of his brother:

    data is read in the update collective run without taking the sequence into accountand then transferred to the BW delta queues.


    image

    Fig.5</b>: (Unserialized) V3 Delta update mechanism


    It’s pleonastic to say that

    all (performance) problems related to the serialized V3 update can’t applyto the unserialized one !

    However, already known

    V2 dependencykeep on subsist.

    When this method can be used ?

    Only if it’s irrelevant whether or not the extraction data is transferred to BW in exactly the same sequence (serialization) in which the data was generated in R/3 (thanks to a specific design of data targets in BW and/or because functional data flow doesn’t require a correct temporal sequence).

    !https://weblogs.sdn.sap.com/weblogs/images/21406/CallSequence.gif|height=378|alt=image|width=576|src=https://weblogs.sdn.sap.com/weblogs/images/21406/CallSequence.gif|border=0!

    Fig.6</b>: Comparison among call function hierarchies involved in different update methods



    h4. Little recap of essential points to consider in migration process


    If you want to select a new update method, you have to implement specific OSS notes, otherwise, even if you have selected another update method, data will still be written to the V3 update and it can no longer be processed !

    Here is an OSS collection related to update method switch divided for application:

      1. PURCHASING (02) -> OSS note 500736
      2. INVENTORY MANAGEMENT (03) -> OSS note 486784
      3. PRODUCTION PLANNING AND CONTROL (04) -> OSS note 491382
      4. AGENCY BUSINESS (45) -> OSS note 507357

    If the new update method of an application is the queued delta, it’s better to have the latest qRFC version installed.

    However, before changing, you must make sure that there are no pending V3 updates (as suggested before, run the RMCSBWCC during a document posting free phase and switch the update method if this program doesn’t return any open V3 updates).

    h4. Early delta initialization in the logistics extraction and final considerations


    Not always on our systems an important downtime is possible in the initialization process during the reconstruction and the delta init request (just thinking when you need to ask a billing stop period…a real nightmare in some company !)

    For this reason, as of PI 2002.1 and BW Release 3.0B, you can use the

    early delta initializationto perform the initialization for selected datasources (just checking in infopackage update mode tab if this function is available): in this way you can readmit document postings in the OLTP system as early as possible during the initialization procedure.

    In fact, if an early delta initialization infopackage was started in BW, data may be written immediately to the delta queue.

    But, if you are working with the queued delta method, using early delta initialization function doesn’t make sense: as described before, it’s the same method definition that permits to reduce downtime phase.

    But leaving aside that, don’t forget that, regardless of the update method selected, it’s ALWAYS necessary to stop any document postings (for the relevant application) during setup tables recompilation run !

    h5. Final considerations


    In the end, just some little personal thoughts…

    After concluding this delta methods overview, it’s clear that

    queued delta will be very probably the most used and popular delta method in Logistic Cockpit: if we consider direct and unserialized ones as exploitable only in specific and not so frequent situations (low delta document occurrences or no serialization needed), queued delta comes as legitimate heir to the throne before occupied by the old ‘serializer’.

    Ok, all the elements are now available: it’s up to you making a right choice of delta method taking in consideration your specific scenario !

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    23 Comments

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    1. Hans Kraft
      This is making sense to me now. Thanks but what do you mean by PI 2002.1 and aRFC? could you please refer me some links or docs. gandaki@gmail.com.

      All these three weblogs are very helpful for consultant like me. Thank you again and keep up the good work in this forum.
      Gandaki

      (0) 
      1. Anonymous
        (0) 
    2. Jkyle Landicho
      Hi Roberto,

      In my opinion, this Blog is far more clear than those offered by SAP itself. Short but well written w/o all the clutters. You can be a good BW instructor!

      Keep it up and more power!    

      (0) 
    3. Martin Stillnerus
      Hi Roberto,

      Many thanks for you Web Logs about LO Cockpit. Much appreciated. A question about your statement:
      “regardless of the update method selected, it’s ALWAYS necessary to stop any document postings (for the relevant application) during setup tables recompilation run !”

      Would it be possible for you to describe why, a little bit closer? I am hoping to be able to avoid a document posting stop in the source system. I thought that, using queued delta, the extraction queue starts to collect docs as soon as the extractor is activated (from LBWE, changing the traffic light to green).
      Would it be possible for you to comment below activity list and tell me where I got it wrong?

      Scenario: Setting up delivery docs (application 12) to an ODS in BW, queued delta as update method.

      1. Activate the data source you want to use (like 2LIS_12_VCITM)

      2. Fill the setup table with historical data for application 12. (If a doc is created during the setup it might be that it is not contained in the setup table but it will be registered in the extraction queue and transferred to BW with my first delta load).

      3. Start a delta init info Package that reads all the docs in the setup table and writes it to my ODS.

      4. Run the extraction collection run for application 12 that fills the data source activated for application 12 in the delta queue (trans RSA7).

      5. Run a delta info package from BW. (If a document is transferred both by the delta init as well as the first delta load, I would like to believe that the ODS will only overwrite itself and not changing the final doc in the active table).

      6. Schedule the extraction collection run as well as the delta load.
      – end –

      I understand that this is not applicable if you load directly to a cube but I do not understand why this wouldn’t work without a doc posting stop loading to a ODS.

      Thanks,

      Martin

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        1. Lori Rogers
          I too would like to hear from you, Roberto, on Martin’s question above. I’m getting pressured to reduce R3 downtime. I’ll be converting from Direct Delta to Queued Delta and will need to be perform a full re-initialization. Thanks.
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          1. Anonymous
            Hi guys,
            if your data model can accept with no problem a staging ODS with an overwriting mechanism, you can try to do not stop document posting since you will have no duplication risk…
            But pay attention on that ODS: not always you can use it without loosing important information (as the complete document history)…
            Bye,
            Roberto
            (0) 
      1. Cesar Menezes
        Martin

        I posted a thread trying to detail your question.
        “How to avoid document posting stop period during restructuring”.
        Link: How to avoid document posting stop period during restructuring

        Also posted three other threads.

        If you have some time, I would appreciate your comments.

        V1, V2, V3 updates
        V1, V2, V3 updates

        Call Functions in Direct Delta, Queued Delta, Unserialized V3 Update
        Call Functions in Direct Delta, Queued Delta, Unserialized V3 Update

        Sequence of operations – Direct Delta, Queued Delta, Unserialized V3 Update
        Sequence of operations – Direct Delta, Queued Delta, Unserialized V3 Update

        Thanks

        César Menezes

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    4. Amit Pal
      This is reference to LO extraction Direct Delta.
      We say That Data is tranferred directly  from Update tables to Delta queue(i.e. RSA7).So how and When Tranfer/Extract structure come into picture.
      (0) 
      1. Anonymous
        Hi dear,
        to find an answer to your question, it’s enough to take a look to the code of the involved FMs used in the extraction steps (for example, in purchasing area): mcex_update_02_v1 and mcex_update_02.
        As you can see, both FMs use (as table components) our extract structures (that is, what we see in RSA6, for example MC02M_0HDR. extract structures for 2lis_02_hdr).
        Hope now is clearer…
        Bye,
        Roberto
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    5. Amit Pal
      Well i understand what is Delta queue in Reference to tranfer from R/3 To BW. But my Question is that , when we Tranfer data from ODS to InfoCube, the data mart Delta queue(RSA7 in BW) comes into play. I wanted to know, How and When this queue is getting filled .
      (0) 
    6. Amit Pal
      Yes Sir

      You are absolutely correct.while transferring data from ODS to BW we Can see data source 8xxxx in RSA7 in OLAP(BW).what are they and how are they getting filled.

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    7. Fernando Ariel Angueira
      Hello Roberto,
      I have one issue, we change extract structure and we did not stop document posting. So to load data we have to delete some documents from OUTBOUND QUEUE, up to the moment the extract structure change.
      Is there any possibility to recover those missing changes to documents?? or at least to know which POs were changed during that time and reload to BW?
      Thanks!
      (0) 
    8. Cesar Menezes
      Roberto

      I posted a question in SDN about V1, V2 and V3 updates.

      Link: V1, V2, V3 updates

      It seems to me that the definition on V1, V2 and V3 sometimes is technical (V1 = Synchronous update, V2 = Asynchronous update, V3 = Batch asynchronous update), sometimes is commercial (V2 associated with LIS, V3 with Serialized/Unserialized V3 Update, V1 with Direct Delta). And they conflict with each other.

      The point is that Figure 5 (Data Flow for Logistic Extraction with V3 Update), showed in Episode Three and also in the power point “New Update Methods for Logistics Extraction with PI 2003.1”, describes the inserting into Update Tables as “V3 Module Call” (wich means batch asynchronous). From what I understood until now, this is much more a “V2 Module Call” (wich means asynchronous, but not batch).

      If you have some time I’d appreciate your comments.

      César Menezes

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    9. Cesar Menezes
      Roberto

      I put all my questions in these threads:

      1) V1, V2, V3 updates
      link: V1, V2, V3 updates

      2) Call Functions in Direct Delta, Queued Delta, Unserialized V3 Update
      link: Call Functions in Direct Delta, Queued Delta, Unserialized V3 Update

      3) Sequence of operations – Direct Delta, Queued Delta, Unserialized V3 Update
      Sequence of operations – Direct Delta, Queued Delta, Unserialized V3 Update

      4) How to avoid document posting stop period during restructuring
      How to avoid document posting stop period during restructuring

      I’m aware that you have a lot of things to do, and, as we say here, with these questions I’m “unloading a watermelons truck” over you.

      Anyway, if you have some time your comments will be usefull not only for me, but also for the people who reads this blog.

      Thanks

      César Menezes

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    10. Peggy Bellmann
      Dear Roberto,

      thanks for the great explanation. That is exactly what I have been looking for. Unfortunately I’m not able to see the pictures. Do you have this somewhere as doc?

      Greetings,
      Peggy

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