$asm = [System.Reflection.Assembly]::LoadWithPartialName("System.Data.OracleClient") 
      
$connectionString = "Тут мое подключение";      
$inputString = "foo";

$oracleConnection = new-object System.Data.OracleClient.OracleConnection($connectionString);
$cmd = new-object System.Data.OracleClient.OracleCommand;
$cmd.Connection = $oracleConnection;

$cmd.CommandText = "isFoo";
$cmd.CommandType = [System.Data.CommandType]::StoredProcedure;

$cmd.Parameters.Add("inputString", [System.Data.OracleClient.OracleType]::VarChar) | out-null;
$cmd.Parameters["inputString"].Direction = [System.Data.ParameterDirection]::Input;
$cmd.Parameters["inputString"].Value = $inputString;
      
$cmd.Parameters.Add("outString", [System.Data.OracleClient.OracleType]::VarChar)  | out-null;  
$cmd.Parameters["outString"].Direction = [System.Data.ParameterDirection]::Output;
    
$oracleConnection.Open();
$cmd.ExecuteNonQuery() | out-null;
$oracleConnection.Close();

$result = $cmd.Parameters["outString"].Value;
write-host "result of isFoo($inputString) is $result" -foregroundcolor yellow;

create or replace PROCEDURE  isFoo (inputString IN  VARCHAR2, outString OUT VARCHAR2) IS  
BEGIN
  outString := inputString;
END isFoo;