Every so often I have to extract some data from a source system that changes without warning.
If a column suddenly disappears from a source table my load table will error, probably causing my whole job to stop. WhereScape RED has some really cool functionality to protect against this. The Non Mandatory Source Columns feature allows you to flag a load table for extra protection.
This option can be found on the Source Mapping tab of load table properties for database link loads. I turn this option on and usually choose Warning for Exit status when missing columns. When the load table runs via the scheduler, WhereScape RED automatically checks to see which columns in the source table or tables exist. If any source columns don't exist, the table is still loaded and the missing columns are set to NULL.
Other options for the exit status are Error and Success.
I've taken this a step further a couple of times and used After Load column transformations to reset any NULL values to a default value.