This handler is similar to the previous one, except that it treats the whole sheet as a single data source. It is designed exclusively to be used with custom parsers that deal specifically with data sheets. It has similar fields to the Sitecopy CSV source. It you are going to use these, exercise caution - sheets over a few hundred rows have been known to cause outages on sites due to memory limitations. You can split the sheet into multiple smaller sheets and run them in two separate jobs.