All about Dimensions....

Dimension design: A different perspective

by Manohar Delampady 

Version 3

Objective: The objective of this post is to simplify the understanding on dimension designs of an infocube and to decide upon the dimensions based on the repetition of the data held in the dimension tables.

Pre-requisites: An infocube is already created and active, and filled will data, which will be used for analysis of dimension tables.

Dimension to Fact Ratio Computation: This ratio is a percentage figure of the number of records that exists in the dimension table to the number of records in fact table or what percentage of fact table size is a dimension table. Mathematically putting it down, the equation would be as below:

          Ratio = No of rows in Dimension table X 100 / No of rows in Fact Table

Dimension Table Design Concept: We have been reading and hearing over and over again that the characteristics should be added into a dimension if there exists a 1:1 or 1:M relation and they should be in separate dimension if there exists a M:M relation. What is this 1:1 or 1: M? This is the relation which the characteristics share among each other.

For instance if one Plant can have only one Storage Location and one storage location can belong to only one plant at any given point of time, then the relation shared among them is 1:1.

If 1 Functional Location can have many equipment but one equipment can belong to only one functional location then the relation shared between the functional location and Equipment is 1:M.

If 1 sales order can have many materials and one material can exist in different sales orders then there absolutely is no dependence among these two and the relation between these two is many to many or M: M.

Challenges in understanding the relationship: Often we SAP BI consultants depend on the Functional consultants to help us out with the relationship shared between these characteristics / fields. Due to time constraint we generally cannot dedicate time to educate the functional consultants on the purpose of this exercise, and it takes a lot of time to understand this relationship thoroughly.

Scenario: An infocube ZPFANALYSIS had few dimensions which were way larger than the preferred 20% ratio. This had to be redesigned such that the performance was under 20% ratio.

This ratio could be either manually derived by checking the number of entries in the desired dimension table (/BIC/D<infocube name><dimension number>) to the fact table (/BIC/F<Infocube Name> or /BIC/E<Infocube name>) or a program SAP_INFOCUBE_DESIGNS can be executed in SE38 which reports this ratio for all the dimensions, for all the infocubes in the system.

SAP_INFOCUBE_DESIGNS:

We can find from the report that the total number of rows in the fact table is 643850. Dimension 2 (/BIC/DZPFANLSYS2) has around 640430 rows, which is 99% (99.49%)of the fact table rows and Dimension 4(/BIC/DZPFANLSYS4) has around 196250 rows, which is 30%  (30.48%)of the fact table rows.

Infocube ZPFANLSYS:

Approach:

Step 1: Analysis of the dimension table /BIC/DZPFANALSYS2 to plan on reducing the number of records.

/BIC/DZPFANLSYS2

Fact table:

Dimension table holds 1 record more than the fact table.

View the data in the table /BIC/DZPFANLSYS2 (Table related to Dimension 2) in SE12 and sort all the fields. This sorting will help us spot the rows which have repeated values for many columns, which will eventually lead to understanding the relationship between the characteristics (columns in dimension table).

Identifying the relationships:

Once the sorting is done we need to look out for the number of values that repeat across the columns. All the records which repeat could have been displayed in a single row with one dimension id assigned if all the columns had same data. The repetition is a result of one or more columns which contribute a unique value to each row. Such columns if removed from the table then the number of rows in the table will come down.

In the below screenshot I’ve highlighted the rows in green that were repeating themselves with new dimension IDs, as only 2 columns SID_ZABNUM and SID_0NPLDA have new values for every row. These two columns having new values for every row have resulted in rest of the columns repeating themselves and in turn increasing the data size in the dimension table. Hence it can be easily said that these two columns do not belong in this dimension tables, so the related characteristics (ZABNUM and 0NPLDA) need to be removed out of this dimension.
Few rows could be found which repeat themselves for most of the columns, but have a new value once in a while for some columns, as highlighted in yellow in the below screenshot. This indicates that these columns share a 1:M relation with the rest of the columns with repeated rows and these could be left in the same dimension.

Conclusion: The columns marked in green belong to this dimension tables and the columns marked in red needs to be in other dimension tables.

Step 2: Create a copy infocube C_ZPFAN and create new dimensions to accommodate ZABNUM and 0NPLDA.

ZABNUM was added to dimension C_ZPFAN8 and 0NPLDA was added to C_ZPFAN7. These were marked as line item dimensions as they have only one characteristic under them.

Analysed the issue with dimension 4 in the similar way and changed other dimensions to help the situation.

Post changes, loaded the data into the copy infocube C_ZPFAN and found the number of records in the dimension table /BIC/DC_ZPFAN2 to be 40286.

Ratio: 40286 / 657400 * 100 = 6.12 %

SAP_INFOCUBE_DESIGNS:

Dimension2 of the copy infocube: /BIC/DC_ZPFAN2

Even now there a few repeated rows and columns, but the ratio is within 20%. We can create up to 13 dimensions, but it is always better to keep a dimension or two free for future enhancements.

Hope this was helpful.

All About Process Chains....Use of RSWAITSEC Program to introduce delay in the Process Chains

By Mohanavel at scn.sap.com

Objective:    Introducing time delay in the process chain with help of standard SAP provided program RSWAITSEC.

Background:  With the use of interrupt process type in the process chain we can give the fixed delay to the subsequent process types when the interrupt step is reached.  But when we use the standard interrupt process type we have to mention the date and time or event name.

In many cases interrupt step might not help, if suppose an interrupt step is introduce to delay the subsequent processes by a definite period of time, and if all the steps above to the interrupt gets completed early then instead of passing the trigger to the subsequent step after the desired wait time, the interrupt will force the chain to wait till the conditions in the interrupt are satisfied.

In order to achieve the delay in the trigger flow from one process type to another in a process chain without any condition for the fixed time limit or event raise we can use this RSWAITSEC Program.

Scenario:   In our project one of the master data chain is getting scheduled at 23.00IST. This load supplies data to the report which is based on 0CALWEEK. The data load and an abap program in the process chain make use of SY-DATUM, so a load that starts on sunday 23:00 if doesn't complete by 23:59:59 hours (1 hour duration) then the entire data gets wrongly mapped to the next week. .This will cause discrepancy of data.

So it was required to schedule chain at 23:00 IST everyday except sunday, and at 22:45:00IST (15mins earlier) on Sundays.

Different Ways to Achieve the above Situation:

1.        Creating two different process chains and scheduling the 1st process chain at 23.00 IST for Monday to Saturday (Using factory calendar), scheduling the 2nd at 22.45 IST only for Sunday.

Disadvantage of 1st method:

Unnecessarily creating two chains for the same loads, this makes way to have multiple chains in the system.

   2.   Scheduling the same chain at 22.45IST and adding the decision step to find and give interruption of 15mins for Monday to Saturday.  So on Sunday it will  get start at 22.45.

Process Chain with Interrupt Process Type:

Disadvantage of 2nd method:

If suppose you want execute this chain with immediate in other time, then my interruption step will wait until 23.00 IST to get start the load for Monday to Saturday loads.

Better Way of Achieving with RSWAITSEC program:

Scheduling the chain at 22.45 and adding the decision step to find whether its Sunday or other.  If Sunday then next step would be directly to the local chain, if the particular day is between Monday to Saturday then the next step would be with RSWAITSEC program(SAP std program).   In the program variant we have to mention the desired time delay in Secs(900 Secs).

     Compared to above two methods, this will be the  better way to achieve the desired output.  Even though if I run the process chain with start process as         immediate on other than Sunday’s my local chain will not wait until 23.00IST to reach, it will wait for 15mins and it will get triggered. 

       As this is the SAP provided one no need to move any TP for this, even in production we will be able to use directly.

Process chain with RSWAITSEC:

ABAP Process type with RSWAITSEC Program(which shown in the above PC):

Setting the Variant value (required time):

In the variant value we need to mention the desired limit of delay in Seconds.  My requirement is of with 15mins of delay, so I have given 900sec in the variant value.

So we can use this program in any stages of process chain to give the fixed period of delay.

Hope this will be helpful.

All about Process Chains.... Tips

By: Chandiraban singu

Process chain:

A Process chain is a sequence of processes that wait in the background for an event. Some of these processes trigger a separate event that can start other processes in turn.

If you use Process chains, you can

Automate

the complex schedules in BW with the help of the event-controlled processing,

Visualize

the schedule by using network applications, and

Centrally control and monitor

the processes. This article will provide you a few (Seven) tips in the management of Process chain.

http://www.sdn.sap.com/irj/scn/go/portal/prtroot/docs/library/uuid/00a1f389-ec7c-2c10-04bc-9d81b3084171?overridelayout=true

All about Process Chains... in SAP BW Step By Step

By: Anonymous

I want to continue my series for beginners new to SAP BI. In this blog I write down the necessary steps how to create a process chain loading data with an infopackage and with a DTP, activation and scheduling of this chain.

1.)    Call transaction RSPC



 RSPC is the central transaction for all your process chain maintenance. Here you find on the left existing process chains sorted by “application components”.  The default mode is planning view. There are two other views available: Check view and protocol view.
2.)    Create a new process chain
To create a new process chain, press “Create” icon in planning view. In the following pop-Up window you have to enter a technical name and a description of your new process chain.



The technical name can be as long as up to 20 characters. Usually it starts with a Z or Y. See your project internal naming conventions for it.
3.)    Define a start process
After entering a process chain name and description, a new window pop-ups. You are asked to define a start variant.
 


That’s the first step in your process chain! Every process chain does have one and only one starting step. A new step of type “Start process” will be added. To be able to define unique start processes for your chain you have to create a start variant. These steps you have to do for any other of the subsequent steps. First drag a process type on the design window. Then define a variant for this type and you have to create a process step. The formula is:
 Process Type + Process Variant = Process Step!
If you save your chain, process chain name will be saved into table RSPCCHAIN. The process chain definition with its steps is stored into table RSPCPROCESSCHAIN as a modified version.So press on the “create” button, a new pop-up appears:



Here you define a technical name for the start variant and a description. In the n ext step you define when the process chain will start. You can choose from direct scheduling or start using meta chain or API. With direct scheduling you can define either to start immediately upon activating and scheduling or to a defined point in time like you know it from the job scheduling in any SAP system. With “start using meta chain or API” you are able to start this chain as a subchain or from an external application via a function module “RSPC_API_CHAIN_START”. Press enter and choose an existing transport request or create a new one and you have successfully created the first step of your chain.
 4.)    Add a loading step
If you have defined the starting point for your chain you can add now a loading step for loading master data or transaction data. For all of this data choose “Execute infopackage” from all available process types. See picture below:



You can easily move this step with drag & drop from the left on the right side into your design window.A new pop-up window appears. Here you can choose which infopackage you want to use. You can’t create a new one here. Press F4 help and a new window will pop-up with all available infoapckages sorted by use. At the top are infopackages used in this process chain, followed by all other available infopackages not used in the process chain. Choose one and confirm. This step will now be added to your process chain. Your chain should look now like this:



How do you connect these both steps? One way is with right mouse click on the first step and choose Connect with -> Load Data and then the infopackage you want to be the successor.

 

Another possibility is to select the starting point and keep left mouse button pressed. Then move mouse down to your target step. An arrow should follow your movement. Stop pressing the mouse button and a new connection is created. From the Start process to every second step it’s a black line.
5.)    Add a DTP process In BI 7.0 systems you can also add a DTP to your chain. From the process type window ( see above.) you can choose “Data Transfer Process”. Drag & Drop it on the design window. You will be asked for a variant for this step. Again as in infopackages press F4 help and choose from the list of available DTPs the one you want to execute. Confirm your choice and a new step for the DTP is added to your chain. Now you have to connect this step again with one of its possible predecessors. As described above choose context menu and connect with -> Data transfer process. But now a new pop-up window appears.

 
Here you can choose if this successor step shall be executed only if the predecessor was successful, ended with errors or anyhow if successful or not always execute. With this connection type you can control the behaviour of your chain in case of errors. If a step ends successful or with errors is defined in the process step itself. To see the settings for each step you can go to Settings -> Maintain Process Types in the menu. In this window you see all defined (standard and custom ) process types. Choose Data transfer process and display details in the menu. In the new window you can see:



 DTP can have the possible event “Process ends “successful” or “incorrect”, has ID @VK@, which actually means the icon and appears under category 10, which is “Load process and post-processing”. Your process chain can now look like this:




You can now add all other steps necessary. By default the process chain itself suggests successors and predecessors for each step. For loading transaction data with an infopackage it usually adds steps for deleting and creating indexes on a cube. You can switch off this behaviour in the menu under “Settings -> Default Chains". In the pop-up choose “Do not suggest Process” and confirm.



Then you have to add all necessary steps yourself.
6.)    Check chain
Now you can check your chain with menu “Goto -> Checking View” or press the button “Check”. Your chain will now be checked if all steps are connected, have at least one predecessor. Logical errors are not detected. That’s your responsibility. If the chain checking returns with warnings or is ok you can activate it. If check carries out errors you have to remove the errors first.
7.)    Activate chain
After successful checking you can activate your process chain. In this step the entries in table RSPCPROCCESSCHAIN will be converted into an active version. You can activate your chain with menu “Process chain -> Activate” or press on the activation button in the symbol bar. You will find your new chain under application component "Not assigned". To assign it to another application component you have to change it. Choose "application component" button in change mode of the chain, save and reactivate it. Then refresh the application component hierarchy. Your process chain will now appear under new application component.
8.)    Schedule chain
After successful activation you can now schedule your chain. Press button “Schedule” or menu “Execution -> schedule”. The chain will be scheduled as background job. You can see it in SM37. You will find a job named “BI_PROCESS_TRIGGER”. Unfortunately every process chain is scheduled with a job with this name. In the job variant you will find which process chain will be executed. During execution the steps defined in RSPCPROCESSCHAIN will be executed one after each other. The execution of the next event is triggered by events defined in the table.  You can watch SM37 for new executed jobs starting with “BI_” or look at the protocol view of the chain.
9.)    Check protocol for errors
You can check chain execution for errors in the protocol or process chain log. Choose in the menu “Go to -> Log View”. You will be asked for the time interval for which you want to check chain execution. Possible options are today, yesterday and today, one week ago, this month and last month or free date. For us option “today” is sufficient.
Here is an example of another chain that ended incorrect:
 

On the left side you see when the chain was executed and how it ended. On the right side you see for every step if it ended successfully or not. As you can see the two first steps were successfull and step “Load Data” of an infopackage failed. You can now check the reason with context menu “display messages” or “Process monitor”. “Display messages” displays the job log of the background job and messages created by the request monitor. With “Process monitor” you get to the request monitor and see detailed information why the loading failed. THe logs are stored in tables RSPCLOGCHAIN and RSPCPROCESSLOG. Examining request monitor will be a topic of one of my next upcoming blogs.


 10.) Comments
Here just a little feature list with comments.
- You can search for chains, but it does not work properly (at least in BI 7.0 SP15).
- You can copy existing chains to new ones. That works really fine.
- You can create subchains and integrate them into so-called meta chains. But the application component menu does not reflect this structure. There is no function available to find all meta chains for a subchain or vice versa list all subchains of a meta chain. This would be really nice to have for projects.
- Nice to have would be the possibility to schedule chains with a user defined job name and not always as "BI_PROCESS_TRIGGER".
But now it's your turn to create process chains.