This issue is fixed in Oracle Solaris 11.2.
When performing a network install of Oracle Solaris on a server configured in the BIOS for UEFI Boot Mode, the boot archive takes a long time to load (approximately 40-50 minutes) before the installation starts.
For example, the process shown below could take 40-45 minutes until you see the second "done" displayed:
Welcome to GRUB! 5 4 3 2 1 0 Booting 'Oracle Solaris 11.1.11.3.0' Loading cd0/platform/i86pc/kernel/amd64/unix: 0%...66%...done. Loading cd0/platform/i86pc/amd64/boot_archive: 0%...1%...3%...5%...7%...9%... 11%...12%...14%...16%...18%...20%...22%...24%...25%...27%...29%...30%...32%... 34%...36%...38%...40%...42%...43%...45%...47%...49%...51%...53%...54%...56%... 58%...60%...62%...64%...66%...67%...69%...71%...73%...75%...77%...79%...80%... 82%...84%...85%...87%...89%...91%...93%...95%...97%...99%...done.
This slowness is limited to network installs in UEFI Boot Mode. In general, no workaround is needed and the process will eventually complete. However, if you need to improve the operating system installation time, use an alternate method to install the operating system, such as using an ISO image, USB image, or CD-ROM/DVD.