diff --git a/include/caosdb/file_transmission/download_request_handler.h b/include/caosdb/file_transmission/download_request_handler.h
index 0586c9379c1cf449c85fbcf44f1f213ac2aed945..2cdfbbca139cc184aa6f95d8dad35daef57f445b 100644
--- a/include/caosdb/file_transmission/download_request_handler.h
+++ b/include/caosdb/file_transmission/download_request_handler.h
@@ -3,7 +3,6 @@
 #include "caosdb/entity/v1alpha1/main.pb.h"       // for FileDownloadResponse
 #include "caosdb/file_transmission/file_writer.h" // for FileWriter
 #include "caosdb/handler_interface.h"             // for HandlerTag, Handl...
-#include "caosdb/transaction_status.h"            // for TransactionStatus
 #include <grpcpp/impl/codegen/async_stream.h>     // for ClientAsyncReader
 #include <grpcpp/impl/codegen/client_context.h>   // for ClientContext
 #include <grpcpp/impl/codegen/completion_queue.h> // for CompletionQueue
diff --git a/include/caosdb/file_transmission/upload_request_handler.h b/include/caosdb/file_transmission/upload_request_handler.h
index ca7123babc13d53eada37c25905778e054496538..440f8b56de691cf48da103be554c9429024d3d4a 100644
--- a/include/caosdb/file_transmission/upload_request_handler.h
+++ b/include/caosdb/file_transmission/upload_request_handler.h
@@ -3,7 +3,6 @@
 #include "caosdb/entity/v1alpha1/main.pb.h"       // for FileUploadRequest
 #include "caosdb/file_transmission/file_reader.h" // for FileReader
 #include "caosdb/handler_interface.h"             // for HandlerTag, Handl...
-#include "caosdb/transaction_status.h"            // for TransactionStatus
 #include <cstdint>                                // for uint64_t
 #include <grpcpp/impl/codegen/async_stream.h>     // for ClientAsyncWriter
 #include <grpcpp/impl/codegen/client_context.h>   // for ClientContext
diff --git a/src/caosdb/file_transmission/download_request_handler.cpp b/src/caosdb/file_transmission/download_request_handler.cpp
index 214ac6eeaa1be9986bc4ed92c6df19f3e1b5561b..68dfff32c7cae61b41c1b70aeef51b8530b6a11e 100644
--- a/src/caosdb/file_transmission/download_request_handler.cpp
+++ b/src/caosdb/file_transmission/download_request_handler.cpp
@@ -1,8 +1,8 @@
 #include "caosdb/file_transmission/download_request_handler.h"
-#include "caosdb/exceptions.h"                         // for Exception
 #include "caosdb/logging.h"                            // for CAOSDB_LOG_TRACE
 #include "caosdb/protobuf_helper.h"                    // for get_arena
 #include "caosdb/status_code.h"                        // for GENERIC_RPC_E...
+#include "caosdb/transaction_status.h"                 // for TransactionStatus
 #include <boost/filesystem/path.hpp>                   // for operator<<, path
 #include <boost/log/core/record.hpp>                   // for record
 #include <boost/log/detail/attachable_sstream_buf.hpp> // for basic_ostring...
@@ -24,16 +24,13 @@
 
 namespace caosdb::transaction {
 using caosdb::StatusCode;
-using caosdb::exceptions::AuthenticationError;
-using caosdb::exceptions::ConnectionError;
-using caosdb::exceptions::Exception;
 using caosdb::utility::get_arena;
 using google::protobuf::Arena;
 
 DownloadRequestHandler::DownloadRequestHandler(
   HandlerTag tag, FileTransmissionService::Stub *stub,
   grpc::CompletionQueue *cq, FileDescriptor file_descriptor)
-  : HandlerInterface(), tag_(tag), stub_(stub), cq_(cq),
+  : tag_(tag), stub_(stub), cq_(cq),
     request_(Arena::CreateMessage<FileDownloadRequest>(get_arena())),
     response_(Arena::CreateMessage<FileDownloadResponse>(get_arena())),
     state_(CallState::NewCall), file_descriptor_(std::move(file_descriptor)),
diff --git a/src/caosdb/file_transmission/upload_request_handler.cpp b/src/caosdb/file_transmission/upload_request_handler.cpp
index 78e199155776396ec6aa84cb6bf867c3d7e5d40a..7cf31c0304540e1f86df7624a0318dfb84d6db91 100644
--- a/src/caosdb/file_transmission/upload_request_handler.cpp
+++ b/src/caosdb/file_transmission/upload_request_handler.cpp
@@ -1,8 +1,8 @@
 #include "caosdb/file_transmission/upload_request_handler.h"
-#include "caosdb/exceptions.h"                         // for Exception
 #include "caosdb/logging.h"                            // for CAOSDB_LOG_ERROR
 #include "caosdb/protobuf_helper.h"                    // for get_arena
 #include "caosdb/status_code.h"                        // for GENERIC_RPC_E...
+#include "caosdb/transaction_status.h"                 // for TransactionStatus
 #include <algorithm>                                   // for min
 #include <boost/filesystem/path.hpp>                   // for operator<<, path
 #include <boost/log/core/record.hpp>                   // for record
@@ -26,9 +26,6 @@
 
 namespace caosdb::transaction {
 using caosdb::StatusCode;
-using caosdb::exceptions::AuthenticationError;
-using caosdb::exceptions::ConnectionError;
-using caosdb::exceptions::Exception;
 using caosdb::utility::get_arena;
 using google::protobuf::Arena;
 
@@ -36,7 +33,7 @@ UploadRequestHandler::UploadRequestHandler(HandlerTag tag,
                                            FileTransmissionService::Stub *stub,
                                            grpc::CompletionQueue *cq,
                                            FileDescriptor file_descriptor)
-  : HandlerInterface(), tag_(tag), stub_(stub), cq_(cq),
+  : tag_(tag), stub_(stub), cq_(cq),
     request_(Arena::CreateMessage<FileUploadRequest>(get_arena())),
     response_(Arena::CreateMessage<FileUploadResponse>(get_arena())),
     state_(CallState::NewCall), file_descriptor_(std::move(file_descriptor)),
diff --git a/src/caosdb/transaction.cpp b/src/caosdb/transaction.cpp
index 59eea7f61a91495bbeceb1b5466ea51eba1f0c33..9a13583174b1be5db61fa89511d2bac5975fe05f 100644
--- a/src/caosdb/transaction.cpp
+++ b/src/caosdb/transaction.cpp
@@ -20,12 +20,12 @@
 #include "caosdb/transaction.h"
 #include "caosdb/entity/v1alpha1/main.grpc.pb.h" // for EntityTransac...
 #include "caosdb/entity/v1alpha1/main.pb.h"      // for TransactionRe...
-#include "caosdb/file_transmission/register_file_upload_handler.h"
-#include "caosdb/file_transmission/upload_request_handler.h"   // Upload...
 #include "caosdb/file_transmission/download_request_handler.h" // Download...
-#include "caosdb/logging.h"         // for CAOSDB_LOG_FATAL
-#include "caosdb/protobuf_helper.h" // for get_arena
-#include "caosdb/status_code.h"     // for StatusCode
+#include "caosdb/file_transmission/file_reader.h"              // for path
+#include "caosdb/file_transmission/register_file_upload_handler.h"
+#include "caosdb/file_transmission/upload_request_handler.h" // Upload...
+#include "caosdb/logging.h"     // for CAOSDB_LOG_FATAL
+#include "caosdb/status_code.h" // for StatusCode
 #include "caosdb/transaction_handler.h"
 #include <algorithm>                                   // for max
 #include <boost/filesystem/path.hpp>                   // for operator<<, path