Hello
   I am beginner to sqlite. my development enviroment is : RTEMS5 + sqlite3.31.1.
And my compile option is  -DSQLITE_MAX_MMAP_SIZE=0 -DSQLITE_DEFAULT_LOCKING_MODE=1 -DSQLITE_ENABLE_MEMSYS5.  and startup config is journal_mode = OFF;
   I use Unix-dotfile as VFS to operate sqlite. I can open db, create table and insert record to  db. but the changes will not be made until I close the db. 
   If I reset the whole system before close the db , everything will be lost, the db size is 0 bytes.

thanks Simon Slavin for reply. 

What makes you think that the changes are not saved ? 
 - I found my test.db file size is 0 bytes. so I think the changes is not saved. but when I use Linux to test, the changes are affected immediatgely.(before I close the db),  

Are you just looking at the database filesize ? Do you see a journal file being made in the same directory ? Does that file also have zero size ?
 - Yes, there is journal file(0 bytes) in the diectory(if I switch PRAGMA journal_mode = OFF, it wouldn't be appear.) 

How are you using SQLite ? Are you making calls to the C API ? Or are you calling a SQLite library for a different programming language ?
 - I am using the C API sqlite3_exec

Are you checking the values returned by your calls to CREATE TABLE and INSERT ? Are the equal to 0 (= SQLITE_OK) ?
 - I have checked the return value, it is SQLITE_OK.

hello Simon
      you are right, I found it is the reason of RTEMS. there is a cache between filesystem and harddisk. I have to use fsync to force data writing to disk after  write method. 
      My question is: is there any kind of flush or sync method in Sqlite I could use ?

See https://sqlite.org/forum/forumpost/b24023c75c84c596

Journal mode OFF disables COMMIT; COMMIT calls fsync() after writing the data. You are bringing this upon yourself.

hello Gunter , thanks for reply
I have tried again, it is still the same. could you check my code?
I might think it is something related to VFS, but I dont know how to fix it.



    sprintf(sql, "INSERT INTO TICKET VALUES (NULL, \'%s\', NULL, NULL, \'%s\',\'%s\', \'%s\',\'%s\');" , uid, date, time, status[ticket->status], type[ticket->type]);

    rc = sqlite3_exec(db, "BEGIN;", NULL, 0, &zErrMsg);
    rc = sqlite3_exec(db, sql, NULL, 0, &zErrMsg);
    if(rc != SQLITE_OK)
    {
        printf("SQL %s INSERT FAILED: %s\n", sql, zErrMsg);
        sqlite3_free(zErrMsg);
    }
    else
    {
#if DEBUG
    	printf("insert ok\n");
#endif
    }
    rc = sqlite3_exec(db, "COMMIT;", NULL, 0, &zErrMsg);

hello Gunter , thanks for reply
I have tried again, it is still the same. could you check my code?
I might think it is something related to VFS, but I dont know how to fix it.


------------- below is for init
	sqlite3_vfs* pDefault = sqlite3_vfs_find("unix-dotfile");
	if(!pDefault)
	{
		printf("cannot find vfs\n");
	}
	sqlite3_vfs_register(pDefault, 1);

    char *zErrMsg = 0;
    char* name = cJSON_GetObjectItem(products->handle, "item")->valuestring;
    int rc = sqlite3_open("./test.db", &db);

	if( rc ){
	  printf( "Can't open database: %s\n", sqlite3_errmsg(db));
	  return FALSE;
	}else{
	  printf( "Opened database successfully\n");
	}


    char* sql = "CREATE TABLE if not exists TICKET("  \
      "ID             INTEGER PRIMARY KEY AUTOINCREMENT  NOT NULL," \
      "UIDTID         VARCHAR(24)  ," \
      "EPC            VARCHAR(124)  ," \
      "SN             VARCHAR(12) ,   " \
      "DATE           VARCHAR(8)   NOT NULL," \
      "TIME           VARCHAR(8)   NOT NULL," \
      "STATUS         VARCHAR(8)   NOT NULL," \
      "TYPE           VARCHAR(8)   NOT NULL" \
       ");";   


    rc = sqlite3_exec(db, sql, NULL, 0, &zErrMsg);
    if(rc != SQLITE_OK)
    {
        printf("DB: %s\n", zErrMsg);
        sqlite3_free(zErrMsg);
        return FALSE;
    }
    else
    {
    	printf("table created\n");
    }




-------------below is for insert

    sprintf(sql, "INSERT INTO TICKET VALUES (NULL, \'%s\', NULL, NULL, \'%s\',\'%s\', \'%s\',\'%s\');" , uid, date, time, status[ticket->status], type[ticket->type]);

    rc = sqlite3_exec(db, "BEGIN;", NULL, 0, &zErrMsg);
    rc = sqlite3_exec(db, sql, NULL, 0, &zErrMsg);
    if(rc != SQLITE_OK)
    {
        printf("SQL %s INSERT FAILED: %s\n", sql, zErrMsg);
        sqlite3_free(zErrMsg);
    }
    else
    {
#if DEBUG
    	printf("insert ok\n");
#endif
    }
    rc = sqlite3_exec(db, "COMMIT;", NULL, 0, &zErrMsg);

Check if your VFS filesystem implementation xSync function gets called.

If yes, then the problem is in the VFS. If no, then your settings are preventing SQLite from calling it.

Maybe you are not committing your transaction. Since everybody else is successfuly using SQLite, you must be doing something wrong. Which we cannot discern until you show us your code, or at least the statements you are executing.

Did you read up on the journal mode? 

https://sqlite.org/pragma.html#pragma_journal_mode

"The OFF journaling mode disables the atomic commit and rollback capabilities of SQLite. ... If the application crashes in the middle of a transaction when the OFF journaling mode is set, then the database file will very likely go corrupt."

I would say exiting the program without closing the database connection has a similar effect as crashing the application. Maybe your rtems implementation of the unix-none VFS is keeping data from hitting the storage device or setting the yournal mode is avoiding calls to flush or whatever.

If you have an ltrace or strace utility to capture system calls you should be able to see the difference.

Might check for success after writes using one of these:
sqlite3_changes(hDB) 
sqlite3_total_changes(hDB)