Use a java activity step or create a function... rough code:

  // Your code starts after this line. DO NOT REMOVE THIS LINE
  java.sql.Connection conn = null;
  java.sql.Statement stmt = null;
 
  String url = "";
  String username = "";
  String password = "";
  String key = "";
 
  boolean hadError = false;
 
  byte streamBytes[];
 
  try
  {
    Class.forName("oracle.jdbc.OracleDriver");
    url = "jdbc:oracle:thin:@//your.dbserver.com:dbport/dbschema";
    username = "dbuserid";
    password = "dbpassword";
    conn = java.sql.DriverManager.getConnection(url, username, password);
  }
  catch(Exception ex)
  {
    oLog.infoForced("Exception - "+ex.toString());
    hadError = true;
  }
 
  if(!hadError)
  {
    try
    {
      key = tools.getParamValue("inputkey");
      StringBuffer sql = new StringBuffer();
      sql.append("select pzpvstream from your_table where pzinskey = '"+key+"'");
      stmt = conn.createStatement(java.sql.ResultSet.TYPE_SCROLL_INSENSITIVE, java.sql.ResultSet.CONCUR_UPDATABLE);
      java.sql.ResultSet rs1 = stmt.executeQuery(sql.toString());
      rs1.next();
 
      java.sql.Blob streamBlob = rs1.getBlob(1);
      long streamLength = streamBlob.length();
      streamBytes = streamBlob.getBytes(1L, (int)streamLength);
 
      rs1.close();
      stmt.close();
      conn.close();
    }
    catch(Exception ex)
    {
      oLog.infoForced("Exception - "+ex.toString());
    }
  }

  // Your code ends prior to this line. DO NOT REMOVE THIS LINE