DB_HEAP access method with db_hotbackup utility

Question

I open a Db handle with DB_HEAP access method and do nothing about it . When first created , the db file is 8kb , but after excuting db_hotbackup utility the db file is 4kb. if I do db_hotbackup under the failover environment , BDB give me an error message :
     db_hotbackup: Backup Failed: BDB0075 DB_PAGE_NOTFOUND: Requested page not found
     db_hotbackup: BDB5043 HOT BACKUP FAILED!
Other access method is ok . I try to set the Db pagesize 8kb but still wrong .
I think a db file is bigger than a page size. So it's hard to understand.
Thanks

Answer 1

Sorry about mix the two problems. Let me make it clearly :
1 .Create an Environment contains an empty DB_HEAP database file with the code below.
     1.1 compile the code and mkdir "fileHome" for Environment direcotory,
     1.2 execute the program
2. execute { db_hotbackup -h ./fileHome -b ./failover } . and in failover directory the database file will  become smaller than it in Environment direcotry.
3. chang code { const char* fileHome = "fileHome"; } to { const char* fileHome = "failover"; }
4. compile the changed code and execute again.( for creating region files in the failover directory)
5. execute { db_hotbackup -h ./failover -b ./failover_back } after this we can see the wrong message :
           db_hotbackup: Backup Failed: BDB0075 DB_PAGE_NOTFOUND: Requested page not found
           db_hotbackup: BDB5043 HOT BACKUP FAILED!
The problem I said on the previous time is I try to insert some record to the database but failed. I just wonder if this BDB version is not supportint DB_HEAP access method.
The code is :
#include<iostream>
#include<cstring>
#include<cstdlib>
#include"db_cxx.h"
int main()
  u_int32_t env_flags = DB_CREATE |
       DB_INIT_LOCK |
       DB_INIT_LOG |
       DB_INIT_TXN |
       DB_INIT_MPOOL;
  u_int32_t db_flags = DB_CREATE | DB_AUTO_COMMIT;
  const char* fileHome = "fileHome";
  const char* filename = "simpletxn.db";
  Db *dbp = NULL;
  DbEnv myEnv(0);
  try{
  myEnv.open(fileHome,env_flags,0);
  dbp = new Db(&myEnv,0);
  dbp->set_pagesize(8 * 1024);
  dbp->open(0,
   filename,
   NULL,
   DB_HEAP,
   db_flags,
   0);
  }catch(DbException& e){
  std::cerr<<"error when opening environment and database: "<<filename<<","<<fileHome<<std::endl;
  std::cerr<<e.what()<<std::endl;
  try{
  if(dbp != NULL)
  dbp->close(0);
  myEnv.close(0);
  }catch(DbException& e){
  std::cerr<<"error when closing environment and database: "<<filename<<","<<fileHome<<std::endl;
  std::cerr<<e.what()<<std::endl;
  return 0;
Thanks !!!