How did you handle error handling?
Posted on: 12/21/2011
Use of filter to remove the existing records so only the non-existing will Flow through.
Basic error handling can be done using exp transformation to check for the known possible errors, if found give appropriate label to the rows, then pass them through router transformation and direct the rows to the error tables or the target.
Some of the generic checks which are common to most of the mapping e.g. check for zero, null, length etc can be defined as reusable expression transformation which then can used in different mappings.
Informatica Reference 