diff --git a/grpc-testtool/proto/merkle/merkle.proto b/grpc-testtool/proto/merkle/merkle.proto
index 7519288c7..94261d3ea 100644
--- a/grpc-testtool/proto/merkle/merkle.proto
+++ b/grpc-testtool/proto/merkle/merkle.proto
@@ -4,49 +4,52 @@ package merkle;
 
 import "google/protobuf/empty.proto";
 
+// Methods on this service return status code NOT_FOUND if a requested
+// view, iterator or root hash is not found.
 service Merkle {
-    rpc NewProposal(NewProposalRequest) returns (NewProposalResponse);
-    rpc ProposalCommit(ProposalCommitRequest) returns (ProposalCommitResponse);
+  rpc NewProposal(NewProposalRequest) returns (NewProposalResponse);
+  rpc ProposalCommit(ProposalCommitRequest) returns (google.protobuf.Empty);
   
-    rpc NewView(NewViewRequest) returns (NewViewResponse);
-    // The methods below may be called with a view ID that corresponds to either a (committable) proposal
-    // or (non-committable) historical view.
-    rpc ViewHas(ViewHasRequest) returns (ViewHasResponse);
-    rpc ViewGet(ViewGetRequest) returns (ViewGetResponse);
-    rpc ViewNewIteratorWithStartAndPrefix(ViewNewIteratorWithStartAndPrefixRequest) returns (ViewNewIteratorWithStartAndPrefixResponse);
-    rpc ViewRelease(ViewReleaseRequest) returns (google.protobuf.Empty);
+  rpc NewView(NewViewRequest) returns (NewViewResponse);
+  // The methods below may be called with an ID that corresponds to either a (committable) proposal
+  // or (non-committable) historical view.
+  rpc ViewHas(ViewHasRequest) returns (ViewHasResponse);
+  rpc ViewGet(ViewGetRequest) returns (ViewGetResponse);
+  rpc ViewNewIteratorWithStartAndPrefix(ViewNewIteratorWithStartAndPrefixRequest) returns (ViewNewIteratorWithStartAndPrefixResponse);
+  // Returns status code NOT_FOUND when the iterator is done.
+  rpc IteratorNext(IteratorNextRequest) returns (IteratorNextResponse);
+  rpc IteratorError(IteratorErrorRequest) returns (google.protobuf.Empty);
+  // Iterator can't be used (even to check error) after release.
+  rpc IteratorRelease(IteratorReleaseRequest) returns (google.protobuf.Empty);
+  rpc ViewRelease(ViewReleaseRequest) returns (google.protobuf.Empty);
 }
 
 message NewProposalRequest {
   // If not given, the parent view is the current database revision.
-  optional uint32 parent_view_id = 1;
+  optional uint32 parent_id = 1;
   repeated PutRequest puts = 2;
   // The keys being deleted.
   repeated bytes deletes = 3;
 }
 
 message NewProposalResponse {
-  uint32 proposal_id = 1;
+  uint32 id = 1;
 }
 
 message ProposalCommitRequest {
-  uint32 proposal_id = 1;
-}
-
-message ProposalCommitResponse {
-  CommitError err = 1;
+  uint32 id = 1;
 }
 
 message NewViewRequest {
-  bytes root_id = 1;
+  bytes root_hash = 1;
 }
 
 message NewViewResponse {
-  uint32 view_id = 1;
+  uint32 id = 1;
 }
 
 message ViewHasRequest {
-  uint32 view_id = 1;
+  uint32 id = 1;
   bytes key = 2;
 }
 
@@ -55,27 +58,42 @@ message ViewHasResponse {
 }
 
 message ViewGetRequest {
-  uint32 view_id = 1;
+  uint32 id = 1;
   bytes key = 2;
 }
 
 message ViewGetResponse {
   bytes value = 1;
-  GetError err = 2;
 }
 
 message ViewNewIteratorWithStartAndPrefixRequest {
-  uint32 view_id = 1;
+  uint32 id = 1;
   bytes start = 2;
   bytes prefix = 3;
 }
 
 message ViewNewIteratorWithStartAndPrefixResponse {
-  uint32 iterator_id = 1;
+  uint32 id = 1;
+}
+
+message IteratorNextRequest {
+  uint32 id = 1;
+}
+
+message IteratorNextResponse {
+  PutRequest data = 1;
+}
+
+message IteratorErrorRequest {
+  uint32 id = 1;
+}
+
+message IteratorReleaseRequest {
+  uint32 id = 1;
 }
 
 message ViewReleaseRequest {
-  uint32 view_id = 1;
+  uint32 id = 1;
 }
 
 // TODO import this from the rpcdb package.
@@ -83,20 +101,3 @@ message PutRequest {
   bytes key = 1;
   bytes value = 2;
 }
-
-enum GetError {
-  // ERROR_UNSPECIFIED_GET is used to indicate that no error occurred.
-  ERROR_UNSPECIFIED_GET = 0;
-  ERROR_CLOSED_GET = 1;
-  ERROR_NOT_FOUND = 2;
-}
-
-enum CommitError {
-  // ERROR_UNSPECIFIED_COMMIT is used to indicate that no error occurred.
-  ERROR_UNSPECIFIED_COMMIT = 0;
-  ERROR_CLOSED_COMMIT = 1;
-  ERROR_INVALID = 2;
-  ERROR_COMMITTED = 3;
-  ERROR_PARENT_NOT_DATABASE = 4;
-  ERROR_NON_PROPOSAL_ID = 5;
-}