irb(main):004:0> require 'ruby-oci8'
LoadError: Cannot find OCI.DLL in PATH.
from C:/tools/ruby23/lib/ruby/gems/2.3.0/gems/ruby-oci8-2.2.7-x64-mingw32/lib/oci8/check_load_error.rb:42:in `check_os_specific_load_error'
from C:/tools/ruby23/lib/ruby/gems/2.3.0/gems/ruby-oci8-2.2.7-x64-mingw32/lib/oci8/check_load_error.rb:138:in `check_load_error'
from C:/tools/ruby23/lib/ruby/gems/2.3.0/gems/ruby-oci8-2.2.7-x64-mingw32/lib/oci8.rb:110:in `rescue in <top (required)>'
from C:/tools/ruby23/lib/ruby/gems/2.3.0/gems/ruby-oci8-2.2.7-x64-mingw32/lib/oci8.rb:114:in `<top (required)>'
from C:/tools/ruby23/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from C:/tools/ruby23/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from C:/tools/ruby23/lib/ruby/gems/2.3.0/gems/ruby-oci8-2.2.7-x64-mingw32/lib/ruby-oci8.rb:1:in `<top (required)>'
from C:/tools/ruby23/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:127:in `require'
from C:/tools/ruby23/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:127:in `rescue in require'
from C:/tools/ruby23/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:40:in `require'
from (irb):4
from C:/tools/ruby23/bin/irb.cmd:19:in `<main>'