mco_trans_optimistic_threshold

Control the MVCC Transaction Manager behavior with respect to the number of conflicts.

Prototype

 
    void mco_trans_optimistic_threshold( /*IN*/ mco_db_h db,
                         /*IN*/ int max_conflicts_percent,
                         /*IN*/ int disable_period );
 

Arguments

Description

This function helps optimization of MVCC performance. It controls the MVCC Transaction Manager behavior with respect to the number of conflicts (MVCC works best when the number of conflicts is small and poorly when there are many conflicts). The function sets two related parameters: max_conflicts_percent and disable_period. During the commit the MVCC Transaction Manager increments its internal “conflicts counter” (n_conflicts) if a conflict is detected and increments its internal successful "commit counter" (n_commits) otherwise. Furthermore, if the following condition holds:

     
    n_conflicts/(n_conflicts + n_commits)*100 > max_conflicts_percent
     

the subsequent READ_WRITE transactions up to the number specified in parameter disable_period, are executed in “exclusive mode” (only one READ_WRITE transaction at a time). Note that this does not affect READ_ONLY transactions—they are executed in parallel with READ_WRITE transactions and with other READ_ONLY transactions.

By default this optimization is turned off, or in other words max_conflicts_percent = 100%.

Return Codes

Example

 
    Application snippet:
        
     
    const char * dbname = "SimpleDb";
     
    int main(int argc, char* argv[])
    {
        mco_db_h db;
        MCO_RET rc;
        mco_device_t       dev;
        mco_db_params_t    db_params;
         
        ...
        rc = mco_db_open_dev( dbname, simple_get_dictionary(), &dev, 1, &db_params );
        if ( MCO_S_OK != rc )
        {
            rc = mco_db_connect(  dbname, &db );
            ...
            mco_trans_optimistic_threshold( db, 10, 10);  
            ...
        }
        ...
    }
     
 

Files