Informatica ETL Interview Questions and Answers – Part 3
Informatica Interview Questions & Answers:
P. How DTM buffer size and buffer block size are related?
- The number of buffer blocks in a session = DTM Buffer Size / Buffer Block Size. Default settings create enough buffer blocks for 83 sources and targets. If the session contains more than 83, you might need to increase DTM Buffer Size or decrease Default Buffer Block Size.
- (total number of sources + total number of targets)* 2] = (session buffer blocks)
- (session Buffer Blocks) = (.9) * (DTM Buffer Size) / (Default Buffer Block Size) * (number of partitions)
Q. Difference between shortcut and reusable transformation?
- A shortcut is a reference (link) to an object in a shared folder, these are commonly used for sources and targets that are to be shared between different environments / or projects. A shortcut is created by assigning ‘Shared’ status to a folder within the Repository Manager and then dragging objects from this folder into another open folder; This provides a single point of control / reference for the object – multiple projects don’t all have import sources and targets into their local folders.
- A reusable transformation is usually something that is kept local to a folder, examples would be the use of a reusable sequence generator for allocating warehouse Customer Id’s which would be useful if you were loading customer details from multiple source systems and allocating unique ids to each new source-key. Many mappings could use the same sequence and the sessions would all draw from the same continuous pool of sequence numbers generated.
R. What are the types of groups in Router transformation?
- Input Group.
- Output Group.
- The designer copies property information from the input ports of the input group to create a set of output ports for each output group.
- User defined Group.
- Default group.
- One cannot modify or delete default groups.
S. What are the out put files that the Informatica server creates during the session running?
- Informatica server log: Informatica server (on UNIX) creates a log for all status and error messages (default name:pm.server.log). It also creates an error log for error messages. These files will be created in Informatica home directory.
- Session log file: Informatica server creates session log file for each session. It writes information about session into log files such as initialization process, creation of sql commands for reader and writer threads, errors encountered and load summary. The amount of detail in session log file depends on the tracing level that you set.
- Session detail file: This file contains load statistics for each target in mapping. Session detail includes information such as table name, number of rows written or rejected. We can view this file by double clicking on the session in monitor window.
- Performance detail file: This file contains information known as session performance details which helps you where performance can be improved. To generate this file select the performance detail option in the session property sheet.
- Reject file: This file contains the rows of data that the writer does not write to targets.
- Control file: Informatica server creates control file and a target file when you run a session that uses the external loader. The control file contains the information about the target flat file such as data format and loading instructions for the external loader.
- Post session email: Post session email allows you to automatically communicate information about a session run to designated recipients. U can create two different
messages. One if the session completed successfully the other if the session fails.
- Indicator file: If u use the flat file as a target, you can configure the Informatica server to create indicator file. For each target row, the indicator file contains a number to indicate whether the row was marked for insert, update, delete or reject.
- Output file: If session writes to a target file, the Informatica server creates the target file based on file properties entered in the session property sheet.
- Cache files: When the Informatica server creates memory cache it also creates cache files. For the following circumstances Informatica server creates index and data cache files.