For a D3 virtual machine, all printers are treated as serial printers, even if they are parallel. The difference is handled transparently by UNIX. Therefore, the D3 startptr command must always use the s printer type, and never use the p printer type.
A printer can be shared between UNIX and D3, so that both D3 and UNIX users can access it transparently. On a D3 virtual machine, both shared and reserved printers can coexist. This approach allows users to take advantage of D3 spooler features like alignment, hold files, and multiple copies, while still utilizing the UNIX spooler for final output. If such D3 spooler functionality is not required, it is possible to spool data directly to the UNIX spooler bypassing the D3 printer processor altogether.