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SIMPLELOAD - Elementary 'last phase' solution for ETL
    by Ludek Bob Jankovsky, 31-May-2017 (ETL PATTERNS)
Despite on poorest of the solution in comparison to true metadata driven ETL, I often meet transformations realized as views with almost the same format as the target table, followed by the pattern based implementation of the final stage - loading the transformed source data into target table, considering current data and maintaining history.
I have to admit the smart approach is proper for small and quick win solutions.
For easy implementation I scripted a skeleton of the last phase load element based on data dictionary information, supporting the most common patterns. ...more
ETL and the ORA-01502: index *** or partition of such index is in unusable state error, ORA-14063
    by Ludek Bob Jankovsky, 02-Nov-2016 (ORACLE STUFFS)
Especially in huge ETL processes we often increase efficiency of the process by setting some indexes on the target table UNUSABLE. That way we speed-up active operations such as inserts and merges into the table with unusable indexes, but the ORA-01502 error can back-stab us in some phases of the process.
We should be worried about reading operations what we can slow down (sometimes even freeze) by lack of the unusable index, but most of ETL operations are provided in an exclusive time period. By the other hand many concurrent ETL processes and even most overall analytical queries do not need indexes for its work.
However, time after time it happens, the error mentioned above appears in the process. ...more
Simpletask is under the UPL license now
    by Ludek Bob Jankovsky, 29-Oct-2016 (HEAP WORKFLOW)
To make all the license stuff clearer in the case of the Simpletask solution, the UPL - Universal permissive license has been applied for all parts of the software and documentation published on this site under the Simpletask name.
Differently from plain Copyleft license it allows easier incorporation of the software and parts of the software into Larger works without obligation of using the same Copyleft license for these larger works.  ...more
APEX - Downloading files
    by Ludek Bob Jankovsky, 11-Jan-2016 (ORACLE STUFFS)
Using APplication EXpress as a simple GUI cover for Matadata based generators of XML and SQL files led me to task to download these files.
Browsing over various helps I decided to add another one to the rubbish.
There are two basic scenarios:
1. We want to download result of PL/SQL method (function) directly to client machine, or
2. We want to download generated codes from stage - some storage of files prepared for download.  ...more
Real-time ETL patterns and how to piss to pit
    by Ludek Bob Jankovsky, 16-Mar-2014 (ETL PATTERNS)
Recently I published an article about real-time ETL. Designing it we hit on several challenges and various different approaches. To be certain, we speak about Real-time ETL realizing Data integration of sources, not a Service integration. We have to react on smallest changes in source data and propagate the changes to transformed target Data structure. Advantages and disadvantages I described in previous article. ...more
Edges of Real-time ETL
    by Ludek Bob Jankovsky, 11-Jan-2014 (ETL PATTERNS)
Nowadays Real-time and message based ETL take more significant place in IT infrastructure. Differently from Messaging based operational data, in the Real-time approach target data are refreshed based on changes of source data in source systems. That uses means what was earlier often used for replication of data. Differently from replication, realtime ETL is hardly 1:1 but the transformation takes place in the process. Real-time ETL brings many limitation in comparison to standard batch ETL. ...more
XML Import and export utility for SIMPLETASK
    by Ludek Bob Jankovsky, 25-Aug-2013 (HEAP WORKFLOW)
According to principle of maintaining Logical process separately from physical implementation in SIMPLETASK the Export / Import format is necessary.
Following Add-on package contains API for import XML format. The primary intention is to use the feature for importing metadata generated from Logical process model, but it also can be used to archive physical metadata or to transfer them between environments. ...more
APEX GUI for SIMPLETASK heap workflow
    by Ludek Bob Jankovsky, 10-Jul-2013 (HEAP WORKFLOW)
Simpletask Heap Workflow is a simple Oracle based solution for ETL process management based on Oracle DBMS_SCHEDULER and Heap Workflow principles. Now we present APEX GUI, allowing to manipulate metadata and operate ETL easier way than using the PL/SQL based API only. ...more
Heap Workflow
    by Ludek Bob Jankovsky, 29-Jun-2013 (HEAP WORKFLOW)
Long ago when I started to design ETL systems I realized, that robust ETL process management is as important as any other pillar of ETL approach.
Most current workflow systems are focused to easy visualization in structured form.
Structured workflow systems are good for simple process management. I have never seen ETL system with just a little focus on robustness and performance. For that you need a fine grain heap based workflow system allowing to use operational research methods.

What's different?
When you put task into structured workflow, you wire it in certain place to be exacuted at. In heap workflow you put all task in one heap and define constraints of their executions.
The constraints are of following types:
  • Predecessor dependency (solves dependencies comming from referential integrity, data rediness etc.)
  • Resource consumption (solves system resource balancing, exclusivity of filling certain segments and finally using pending resource consumption it can solve temporarily disability of certain objects)
  • Condition function (solves additional timing requirement, branches, skips etc.)
Use data type arithmetic to convert from 'Timestamp' world to 'Date' world and opposite way
    by Ludek Bob Jankovsky, 09-Mar-2013 (ORACLE STUFFS)
There is not straight conversion between the TIMESTAMP and DATE datatypes. Easy way to 'misuse' the standard data type arithmetic to do particular conversions in our queries.
Following article will briefly explain the ways. ...more
Aging table - drop column of partitioned table with compressed old partitions
    by Ludek Bob Jankovsky, 11-Nov-2012 (ORACLE STUFFS)
Using fast aging data (fact tables, logs) you will have to consider some kind of aging strategies like partitioning by time slices, maintaining old partitions compressing them, moving them to slower storage or dropping them at the end. One of factor considered during decision COMPRESS - NO COMPRESS is potential problem of dropping column from table. That is impossible while table or some partitions are compressed. Uncompress all the partitions of huge aged table can make space difficulties. Following solution avoid the problem and offer robust way how to drop column from aged table with compressed partitions. ...more
Usage of SUBQUERY_PRUNING undocumented hint
    by Ludek Bob Jankovsky, 20-Sep-2011 (ORACLE STUFFS)
There are cases when you want to merge data from small table to large one, where partitioning of target table allows to merge data just into last few partitions. Anyway, to know what partitions should be used you need query didstinst partition keys from source table. Oprimizer usually works itself, but if it doesn't, following hint can help. No more words, just an example: ...more
Partitioning sreategy patterns - principal element of Data architecture
    by Ludek Bob Jankovsky, 19-Aug-2011 (ETL PATTERNS)
One of basic chapters in data architecture is a decision about partitioning strategy for particular data layers, table stereotypes and ETL patterns.
Following article will describe basic drivers influencing decisions about partitioning strategy. Details on particular patterns will be linked along.  ...more
Equipartitioning - solution for very large data transformations, but not only for them
    by Ludek Bob Jankovsky, 16-Aug-2011 (ORACLE STUFFS)
There are situations, you want to join two huge tables unselectively for bulk data operartion.
Using NESTED LOOP operation is not effective for big number of rows.
Using HASH JOIN operation is usually effective in such cases, but it has limits when nomber of rows exceeds tens of millions.
EQUIPARTITIONING is a way allowing to make huge bulk operations on hundreds of millions of rows. ...more
Ridiculous (well just for nonparticipants) behaviour of LEFT JOIN in Oracle 11g
    by Ludek Bob Jankovsky, 12-Apr-2011 (ORACLE STUFFS)
There is great feature in Oracle 11g, named Optimizer join elimination. It's designed to reduce effort of database following way:
When there is a Left outer joined table in query, and no column from the table used in result set, optimizer simplifies query and doesn't access the outer joined table - as not necessary.
It sounds great, doesn't it?
Well, it would sound well, if there is no bug.  ...more
Rigid Exchange Partition Data Acquisition approach
    by Ludek Bob Jankovsky, 05-Feb-2010 (ETL PATTERNS)
There are several ways to support consistency of data warehouses and data marts within business hoursperiod. In standard simple approaches it usually suppresses loading time window to really short period between readiness of source data and required readiness of target data. Following approach is just another way allowing keep all data in the mart consistent at the moment, anyway I consider it as an interesting stuff. ...more
Unpivot in the Oracle 10g
    by Ludek Bob Jankovsky, 20-Apr-2009 (ORACLE STUFFS)
Unpivot operation available in Oracle 11g raised wave of interest about the same functionality in the 10g version of Oracle. Unfortunately there is just a workaround available. ...more
TBD STATUS indexing in Oracle
    by Ludek Bob Jankovsky, 08-Mar-2009 (ORACLE STUFFS)
It is not about a special type of index. That is just a technique of indexing columns indicating status TO BE DONE. What is common for such cases:
  • One or several statuses marking few TO BE PROCESSED records.
  • Majority of completed records.
  • Update of field is supposed.
What type of indexing of the field is the best?  ...more
Adding new mandatory columns with specified default 11g vs. 10g
    by Ludek Bob Jankovsky, 28-Feb-2009 (ORACLE STUFFS)
I am sure you have met the issue sometimes. You are adding new mandatory column into very large table. Oracle starts update all rows with default value of the column - like it would never finish. It takes huge amount of time in the data definition phase of migration scripts - not much agreeable issue. Lets see how it has been solved in the 10g (the same as 9i) version of Oracle and what is different in Oracle 11g.  ...more
How to avoid wasting sequences in differential merge pattern
    by Ludek Bob Jankovsky, 25-Feb-2009 (ETL PATTERNS)
In Oracle 10g, 11g getting values from sequences during MERGE behaves a bit strange. Despite you define getting value of sequence directly in a WHEN NOT MATCHED clause, sequence is acquired and wasted even if record is matched. According to docomented behaviour sequence will be acguired for every source record. It is a bad message because of offer usage of mentioned construction in DIFF_MERGE pattern.
Lets see what to do with it. ...more
Tidy your automatically maintained time partition names in 11g
    by Ludek Bob Jankovsky, 25-Feb-2009 (ORACLE STUFFS)
Oracle 11g have introduced new functionality of time interval partitions management. One of disadvantages of new approach are messy ssytem generated names of partitions. It would be pity not to use the new sofisticated approach just because of such issue. Better include simple solition to rename generated partitions based on its metadata definition. ...more
Intra-field list pivot and unpivot
    by Ludek Bob Jankovsky, 17-Feb-2009 (ORACLE STUFFS)
Aside standard unpivot tasks (we create n rows using values from n columns) following unpivot task appears:
One record with coma separated values in a column causes creating several rows, one for each part of the coma separated field.  ...more
Null-ability vs. rigid not null strategies in BI solutions
    by Ludek Bob Jankovsky, 19-Jan-2009 (DATA ARCHITECTURE)
Once several Data warehousing methodologists proposed rigid not-null approach to store data. All the null values has been substituted by not null substitution values despite it is reasonable or not. Like all rigid rules there are both advantages and disadvantages of such approach. Lets see them.  ...more
New time zone for Project managers :)
    by Ludek Bob Jankovsky, 29-Nov-2008 (NEWS)
According to recent experiences new time zone has been implemented. It is regularly used yet, but for better understanding and more clear communication with project managers we attach following transformation table. ...more
ETL process scheduling - failover power
    by Ludek Bob Jankovsky, 06-Nov-2008 (HEAP WORKFLOW)
There are various systems and methods to manage ETL processes. Following article describes failover capability of particular methods. ...more
ETL process scheduling - sample solution for Oracle SIMPLETASK
    by Ludek Bob Jankovsky, 22-Sep-2008 (HEAP WORKFLOW)
Implementing ETL or ELT processes based on PL/SQL modules there is usually one important task in the queue - Schedule execution of atomic modules following internal dependencies and another rules. Enterprise-wide schedulers usually do not fulfill requirements of fine grain dependencies and rules, so they are often used as trigger of ETL batch managed by local ETL scheduler. Most of schedulers built-in into standard ETL tools are too static and rigid, not scaleable. Following solution I call SIMPLETASK, because it is simple by use method despite of teh powers it covers. Following sample is the BASIC version of the solution. Basic, to allow understand better the principle and to be easily included into simplier solutions like small ETL or migration processes. ...more
Data interfaces - independence of particular systems within enterprise
    by Ludek Bob Jankovsky, 18-Sep-2008 (DATA ARCHITECTURE)
There are two basic ways to keep Information systems manageable:
  • Perfect enterprise metadata system (I dream about it but I have never seen it:)
  • Independent systems with defined services and data interfaces more realistic method
Most non success stories producing unmanageable bulks of systems come from attempts to reach the first one. So we will now talk about the second one better. ...more
Metadata driven ETL approach
    by Ludek Bob Jankovsky, 10-Sep-2008 (ETL PATTERNS)
It could be named "Dream about metadata driven ETL". The schema depicted all elements what should participate in the ETL generating process separately to keep the system high manageable. ...more
Unpivot ETL transformation pattern - 10g vs. 11g
    by Ludek Bob Jankovsky, 09-Sep-2008 (ETL PATTERNS)
Unpivot transformation (several columns into several rows) becomes much simplier with Oracle 11g. Lets see. ...more
Partitioning strategy for fact tables - 10g vs. 11g
    by Ludek Bob Jankovsky, 09-Sep-2008 (ORACLE STUFFS)
New features of Oracle 11g simplified management of range partitions allowing INTERVAL partitioning. It allows move part of functionality solved currently by ETL pre-wrappers to default processing of RDBMS defined in Data dictionary metadata. ...more
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