HELP, about DB_AUTO_COMMIT

Question

look at the following codes,
the compilation can be successful, but when executing it,
ret=dbp->put(dbp,txn,&key,&data,0); will return non-zero, if
db_flags is db_create|db_auto_commit, the execution can be normal,
I do not know why,
why can not I set the env to be non-auto commit?
#include <stdio.h>
#include <stdlib.h>
#include <db.h>
#include <string.h>
int main(void)
{ int ret;
u_int32_t db_flags,env_flags;
DB *dbp;
DB_ENV *envp;
DBT key,data;
DB_TXN *txn;
const char *db_home_dir="/home/oracle/env";
const char *file_name="mydb.db";
int k=1;
int d=2;
dbp=NULL;
envp=NULL;
ret=db_env_create(&envp,0);
if(ret!=0)
{fprintf(stderr,"Error create env\n",db_strerror(ret));
  return 0;
env_flags=DB_CREATE|DB_INIT_TXN|DB_INIT_LOCK|DB_INIT_LOG|DB_INIT_MPOOL;
u_int32_t flags;
//ret=envp->set_flags(envp,DB_LOG_INMEMORY,1);
//envp->set_lg_bsize(envp,1024*1024);
//fprintf(stderr,"%s",db_strerror(ret));
ret=envp->open(envp,db_home_dir,env_flags,0);
if(ret!=0) {
fprintf(stderr,"Error open env\n",db_strerror(ret));
return 0;
ret=db_create(&dbp,envp,0);
if(ret!=0)
{ envp->err(envp,ret,"Database creation failed");
return 0;
db_flags=DB_CREATE;
ret=dbp->open(dbp,NULL,file_name,NULL,DB_BTREE,db_flags,0);
if(ret!=0) {
fprintf(stderr,"Error open database\n",db_strerror(ret));
dbp->close(dbp,0);
envp->close(envp,0);
return 0;
memset(&key,0,sizeof(DBT));
memset(&data,0,sizeof(DBT));
key.data=&k;
key.size=sizeof(int);
data.data=&d;
data.size=sizeof(int);
txn=NULL;
ret=envp->txn_begin(envp,NULL,&txn,0);
if(ret!=0)
{ envp->err(envp,ret,"Transaction begin failed");
dbp->close(dbp,0);
envp->close(envp,0);
return 0;
ret=0;
ret=dbp->put(dbp,txn,&key,&data,0);
if(ret!=0)
{ envp->err(envp,ret,"insert failed");
fprintf(stderr,"%s\n",db_strerror(ret));
txn->abort(txn);
dbp->close(dbp,0);
envp->close(envp,0);
return 0;
ret=txn->commit(txn,0);
if(ret!=0)
{ envp->err(envp,ret,"Transaction commit failed");
dbp->close(dbp,0);
envp->close(envp,0);
return 0;
DBC *cursorp;
dbp->cursor(dbp,NULL,&cursorp,0);
int *q;
while(cursorp->c_get(cursorp,&key,&data,DB_NEXT)==0)
{ q=key.data;
printf("%d",*q);
printf("/");
q=data.data;
printf("%d",*q);
printf("\n");
printf("dfdf");
//ret=txn->commit(txn,0);
if(ret!=0)
{envp->err(envp,ret,"Transaction commit failed");
dbp->close(dbp,0);
envp->close(envp,0);
return 0;
cursorp->c_close(cursorp);
dbp->close(dbp,0);
envp->close(envp,0);
return 0;
}

Answer 1

Hi Zhenhua,
The error message being reported is "Transaction specified for a non-transactional database", meaning that the database was not transaction-enabled.
To resolve this you'll have to either use the DB_AUTO_COMMIT flag when opening the database (therefore, an implicit txn) or use an explicit txn (transaction) which will encapsulate the DB->open() call (usually DB_AUTO_COMMIT is preferred for simplicity).
Note that turning on transactions for the environment where the database reside doesn't imply that the database is transaction-enabled.
Regards,
Andrei