Informatica Development Best Practice – Workflow

Workflow Manager default properties can be modified to improve the overall performance and few of them are listed below.    This properties can impact the ETL runtime directly and needs to configured based on :

i)  Source Database
ii) Target Database
iii) Data Volume

Category	Technique
Session Properties	While loading Staging Tables for FULL LOADS,  Truncate target table option should be checked. Based on the Target database and the primary key defined, Integration Service fires TRUNCATE or DELETE statement.Database                  Primary Key Defined                   No Primary KeyDB2                             TRUNCATE                                       TRUNCATE INFORMIX                 DELETE                                              DELETE ODBC                         DELETE                                                DELETE ORACLE                    DELETE UNRECOVERABLE            TRUNCATE MSSQL                       DELETE                                               TRUNCATE SYBASE                     TRUNCATE                                        TRUNCATE Workflow Property “Commit interval” (Default value : 10,000) should be increased for increased for Volumes more than 1 million records.  Database Rollback Segment size should also be updated, while increasing “Commit Interval”. Insert/Update/Delete options should be set as determined by the target population method. Target Option                                   Integration Service Insert                                                   Uses Target update Option Update as Update Update as Insert Update else Insert Update as update                             Updates all rows as Update Update as Insert                               Inserts all rows Update else Insert                            Updates existing rows else Insert
Partition	Maximum number of partitions for a session should be 1.5 times the number of processes in the Informatica server. i.e. 1.5 X 4 Processors = 6 partitions. Key Value partitions should be used only when an even Distribution of data can be obtained.  In other cases, Pass Through partitions should be used. A Source filter should be added to evenly distribute the data between Pass through Partitions. Key Value should have ONLY numeric values. MOD(NVL(<Numeric Key Value>,0),# No of Partitions defined)  Ex: MOD(NVL(product_sys_no,0),6) If a session contains “N” partition, increase the DTM Buffer Size to at least “N” times the value for the session with One partition If the Source or Target database is of MPP( Massively Parallel Processing ), enable Pushdown Optimization.  By enabling this, Integration Service will push as much Transformation Logic to Source database or Target database or FULL ( both ) , based on the settings.  This property can be ignored for Conventional databases.

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Informatica Development Best Practices – Mapping

The following are generally accepted “Best Practices” for Informatica PowerCenter ETL development and if implemented, can significantly improve the overall performance.

Category	Technique		Benefits
Source Extracts	Loading data from Fixed-width files take less time than delimited, since delimited files require extra parsing.  Incase of Fixed width files, Integration service know the Start and End position of each columns upfront and thus reduces the processing time.		Performance Improvement
	Using flat files located on the server machine loads faster than a database located on the server machine.		Performance Improvement
Mapping Designer	There should be a place holder transformation (Expression) immediately after the Source and one before the target.  Data type and Data width changes are bound to happen during development phase and these place holder transformations are used to preserve the port link between transformations.		Best Practices
	Connect only the ports that are required in targets to subsequent transformations.  Also, active transformations that reduce the number of records should be used as early in the mapping.		Code Optimization
	If a join must be used in the Mapping, select appropriate driving/master table while using joins. The table with the lesser number of rows should be the driving/master table.		Performance Improvement
Transformations	If there are multiple Lookup condition, make the condition with the “=” sign first in order to optimize the lookup performance.  Also, indexes on the database table should include every column used in the lookup condition.		Code Optimization
	Persistent caches should be used if the lookup data is not expected to change often.  This cache files are saved and can be reused for subsequent runs, eliminating querying the database.		Performance Improvement
	Integration Service processes numeric operations faster than string operations. For example, if a lookup is done on a large amount of data on two columns, EMPLOYEE_NAME and EMPLOYEE_ID, configuring the lookup around EMPLOYEE_ID improves performance.		Code Optimization
	Replace Complex filter expression with a flag (Y/N). Complex logic should be moved to the expression transformation and the result should be stored in a port.  Filter expression should take less time to evaluate this port rather than executing the entire logic in Filter expression.		Best Practices
	Power Center Server automatically makes conversions between compatible data types which slowdown the performance considerably.  For example, if a mapping moves data from an Integer port to a Decimal port, then back to an Integer port, the conversion may be unnecessary.		Performance Improvement
	Assigning default values to a port; Transformation errors written to session log will always slow down the session performance.  Try  removing default values and eliminate transformation errors.		Performance Improvement
	Complex joins in Source Qualifiers should be replaced with Database views. There won’t be any performance gains, but it improves the readability a lot.  Also, any new conditions can be evaluated easily by just changing the Database view “WHERE” clause.		Best Practices

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Change Data Capture in Informatica

Change data capture (CDC) is an approach or a technique to identify changes, only changes, in the source. I have seen applications that are built without CDC and later mandate to implement CDC at a higher cost. Building an ETL application without CDC is a costly miss and usually a backtracking step. In this article we can discuss different methods of implementing CDC.


Scenario #01: Change detection using timestamp on source rows
In this typical scenario the source rows have extra two columns say row_created_time & last_modified_time. Row_created_time : time at which the record was first created ; Last_modified_time: time at which the record was last modified

1. In the mapping create mapping variable $$LAST_ETL_RUN_TIME of datetime data type
2. Evaluate condition SetMaxVariable ($$LAST_ETL_RUN_TIME, SessionStartTime); this steps stores the time at which the Session was started to $$LAST_ETL_RUN_TIME
3. Use $$LAST_ETL_RUN_TIME in the ‘where’ clause of the source SQL. During the first run or initial seed the mapping variable would have a default value and pull all the records from the source, like: select * from employee where last_modified_date > ’01/01/1900 00:00:000’
4. Now let us assume the session is run on ’01/01/2010 00:00:000’ for initial seed
5. When the session is executed on ’02/01/2010 00:00:000’, the sequel would be like : select * from employee where last_modified_date > ’01/01/2010 00:00:000’, hereby pulling records that had only got changed in between successive runs

Scenario #02: Change detection using load_id or Run_id
Under this scenario the source rows have a column say load_id, a positive running number. The load_id is updated as and when the record is updated

1. In the mapping create mapping variable $$LAST_READ_LOAD_ID of integer data type
2. Evaluate condition SetMaxVariable ($$LAST_READ_LOAD_ID,load_id); the maximum load_id is stored into mapping variable
3. Use $$LAST_READ_LOAD_ID in the ‘where’ clause of the source SQL. During the first run or initial seed the mapping variable would have a default value and pull all the records from the source, like: select * from employee where load_id > 0; Assuming all records during initial seed have load_id =1, the mapping variable would store ‘1’ into the repository.
4. Now let us assume the session is run after five load’s into the source, the sequel would be select * from employee where load_id >1 ; hereby we limit the source read only to the records that have been changed after the initial seed
5. Consecutive runs would take care of updating the load_id & pulling the delta in sequence

In the next blog we can see how to implement CDC when reading from Salesforce.com

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