NAs before, not everyone is aware that the Citrix Universal Printer Driver (UPD) can sometimes generate very large spool files. On a LAN, print jobs with large amounts of data aren’t a big deal, but they can cause massive problems over WAN connections. These large spool files are often print jobs from Adobe PDF documents, but they can also occur with other file types like Word, etc.
How do these print volumes arise, and what can be done about them? Those who understand the issue can reduce print volumes by more than 99%!
The spool file with the Citrix UPD
Users of the Citrix Universal Printer Driver (UPD) use Microsoft's Enhanced Metafile (EMF) format by default. Citrix has enhanced the EMF with various features, including the ability to optimize printouts over WAN connections. This feature was first introduced with Presentation Server 4.5 and has been continuously improved and expanded.
However, despite all the optimizations, spool files can still grow to enormous sizes. This means that the source file—for example, a 9 MB PDF document—will result in a spool file of 450 MB, which may need to go through a WAN connection.
Even if the UPD is set to maximum compression, more than 50% of print data remains, and thus 225 MB of data.
With Riverbed, NetScaler SD-WAN, etc., this can possibly be optimized further, but the real problem lies elsewhere: Microsoft EMF can't handle Raster data can't handle it well, or worse: it increases them even further. Microsoft has described the EMF issue, noting that EMF should turned off will be!
- The size of the EMF spool file can become very large when you print a document that contains a lot of raster data
https://support.microsoft.com/en-us/help/919543/the-size-of-the-emf-spool-file-may-become-very-large-when-you-print-a
Fortunately, Citrix UPD supports not only EMF but also the Microsoft XPS format! The XPS format has no issues with raster data and is also well optimized by Citrix. This means that the Citrix UPD based on XPS also supports the optimizations in the Citrix policies. In the Citrix policy, the XPS format is then given the highest priority and is thus used as the default in all sessions.
Printing the same PDF document as before results in a spool file of exactly 3.77 MB and, by comparison, is negligible at 450/225 MB. A file of this size should also download quickly over a WAN connection.
It is worth considering whether the Citrix UPD should be based on the XPS format as the standard in the future.
