BizTalk 2020 WCF-OracleDB adapter Error

harik98 I would suggest to restart uninstalling previous attempts/unGAC and try the latest 19c unmanaged XCopy client. 

https://www.oracle.com/database/technologies/net-downloads.html

Oracle XCopy unmanaged .NET client installation :

If not default location (ORACLE_HOME\network\admin), create a System Environment Variable for :

  Name:   TNS_ADMIN

  Path (change to your location) :      c:\oracle\network\admin\

CD C:\Oracle\Setup-19x-32bit

:: Install all to 32-bit folder, 32-bit home name. You can omit the last TNS_ADMIN location parameter if using the default location

install.bat all c:\oracle\ora19c32 ora19c32 true true c:\oracle\network\admin

CD c:\oracle\ora19c32

:: Uninstall 32-bit ORAMTS since we will use the 64-bit ORAMTS and you can only have one ORAMTS running.

uninstall.bat ORAMTS ora19c32

CD C:\Oracle\Setup-19x-64bit

install.bat all c:\oracle\ora19c64 ora19c64 true true c:\oracle\network\admin

:: Then manually add these paths to Path System environment variable

c:\oracle\ora19c64

c:\oracle\ora19c32

:: check GAC

gacutil /l | find /I "4.12"

  Oracle.DataAccess, Version=4.122.19.1, Culture=neutral, PublicKeyToken=89b483f429c47342, processorArchitecture=AMD64

  Oracle.DataAccess, Version=4.122.19.1, Culture=neutral, PublicKeyToken=89b483f429c47342, processorArchitecture=x86

  Oracle.ManagedDataAccess, Version=4.122.19.1, Culture=neutral, PublicKeyToken=89b483f429c47342, processorArchitecture=MSIL

:: Add AssemblyRedirect in BizTalk .config files and mmc.exe.config for it to use the latest client

  <runtime>

    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">

      <dependentAssembly>

        <assemblyIdentity name="Oracle.DataAccess" publicKeyToken="89b483f429c47342"  culture="neutral" />

        <bindingRedirect oldVersion="4.0.0.0-4.65535.65535.65535" newVersion="4.122.19.1" />

      </dependentAssembly>

    </assemblyBinding>

  </runtime>