# open( database handle )

> Open the SQL engine with a database handle.

> ### For an overview see page McoSqlEngine

> ### Prototype

>         void open(mco_db_h db);

> ### Arguments

> db | The handle of an opened eXtremeDB database (returned from function `mco_db_connect()`)

> ### Description

> This method opens an eXtremeDB SQL mapper and the McoSqlEngine instance with the database handle in argument `db`.

> ### Returns

> This method throws a RuntimeException in the case of an error.

> ### Example

>         const char * dbname = "SimpleDb";

>         int main(int argc, char* argv[])
>         {
>             MCO_RET rc;
>             sample_memory_t dbmem;
>             McoSqlEngine engine;

>             ...
>             mco_runtime_start();
>             rc = sample_open_database( db_name, SimpleDb_get_dictionary(), DATABASE_SIZE, CACHE_SIZE,
>             MEMORY_PAGE_SIZE, PSTORAGE_PAGE_SIZE, 1, &dbmem );
>             if ( MCO_S_OK == rc )
>             {
>                 rc = mco_db_connect(db_name, &db);
>                 if ( MCO_S_OK == rc )
>                 {
>                     engine.open(db);

>                     ...
>                 }
>             }
>         }