What version of Instant client did you download? Is it 18.104.22.168?It is 22.214.171.124.0 (instantclient-basic-nt-126.96.36.199.0.zip, same for sdk, odbc).
What files are present in c:\instantclient\i386\instantclient_11_2 directory? Can you post the detailed list?Here is the output of dir /s /b instantclient_11_2
It seems that the entry point for OCIDescriptorAlloc is not found in oci.dll, what other functions have undefined referenced?Many other functions have undef ref. Full output of R CMD INSTALL ROracle_1.1-5.tar.gz:
library("Roracle")Error in library("Roracle") : there is no package called 'Roracle'
library("ROracle")Loading required package: DBI
Oracle()Driver name: Oracle (OCI)