Any SQL statements throw exception "General error: 20019 Attempt to initiate a new Adaptive Server operation with results pending [20019] (severity 7)"

Any SQL statements throw exception "General error: 20019 Attempt to
initiate a new Adaptive Server operation with results pending [20019]
(severity 7)" after execution procedure dbo.test2

CREATE TABLE dbo.test01 (
  ttt  int NOT NULL
)
GO


CREATE PROCEDURE dbo.test2
AS
set xact_abort on
BEGIN TRY
      begin tran
      insert into test01 (ttt) values (NULL) /* Here we make SQL error */
      commit
END TRY
BEGIN CATCH
      -- rollback
      return -1 /* Here may be raiserror  */
END CATCH
GO

Why?



--
Best Regards,
Mike Gavrilov.