Eliminating Redundant Custom Formats (or How to Really Take Advantage of PROC SQL, PROC CATALOG, and the DATA Step)
Source: University of Michigan
Custom formats are invaluable to the SAS programmer. Their functionality provides for much more than simply a mechanism for explicitly labeling values in a data set. There can be, however, a major limitation - the DATA step can accommodate only 4,096 formats at a time. It is unlikely that a SAS programmer would generate this many formats in code, but this is not the only method that generates formats. PROC IMPORT and third-party data conversion programs may well generate a distinct custom format for every variable in a data set, and data sets with more than 4,096 variables are not uncommon.