ToC path:

mco_db_extend_dev_t
RT

Extend database memory by adding a memory device within a transaction.

Prototype

 
    MCO_RET	mco_db_extend_dev_t(	/*IN*/ mco_trans_h  t,
                    /*IN*/ mco_device_t * dev );

Arguments

t	The current transaction handle
dev	The device(s) to be added

Description

This function extends the available database memory by adding the specified memory device. Note that whereas mco_db_extend_dev() must be called outside any transaction, mco_db_extend_dev_t() must be called with a READ_WRITE transaction. Typically it is used when a database write operation fails due to low memory.

Return Codes

MCO_S_OK	The database was created successfully
MCO_E_NOINSTANCE	The specified database is not opened
MCO_ERR_TRN	A database transaction error occurred. (eg. The database is already opened by some other thread that has an open transaction.)
MCO_E_ILLEGAL_PARAM	Returned if the device size is too small. The minimum size is runtime configuration- and hardware architecture-dependent. On an x64 platform and configured for 100 connections (default) the minimum size is a little over 1K (1104 bytes) .

Example

 
    Application snippet:

     
    const char * dbname = "SimpleDb";
     
    int main(int argc, char* argv[])
    {
        mco_db_h db;
        MCO_RET rc;
        char *mem = malloc( DBSIZE );
        uint4 total_pages;
        uint4 free_pages;
         
         
        if( (rc = mco_runtime_start()) != MCO_S_OK)
            exit(-1);
             
        rc = mco_db_open( dbname, simpledb_get_dictionary(), mem, DBSIZE, (uint2)PAGESIZE );
        ...
        rc = mco_db_connect(dbname, &db);
        ...
         
        /* If low memory situation detected (see "Auxiliary APIs:  Statistics") */
        mco_db_free_pages(db, &freepages);
        mco_db_total_pages(db, &totalpages );
        if(freepages  < totalpages / 10)
        {
            // yes.  Extend the database
            rc =  mco_trans_start(db, MCO_READ_WRITE, MCO_TRANS_FOREGROUND, &t);
            while ( MAX_SEGMENTS > n_segments )
            {
                dev[n_segments].type         = MCO_MEMORY_CONV;
                dev[n_segments].assignment   = MCO_MEMORY_ASSIGN_DATABASE;
                dev[n_segments].size         = SEGMENT_SIZE;
                dev[n_segments].dev.conv.ptr = (void*)malloc( SEGMENT_SIZE );
                rc = mco_db_extend_dev_t(t, &dev[n_segments]);

                if ( MCO_S_OK != rc ) break;  /* if extend failed exit loop */
                n_segments++;
            }
            if ( MCO_S_OK != rc )
                mco_trans_rollback();
            else
                mco_trans_commit();
            ...
        }
    }

Files

Header file:

mco.h

Source file:

mcodb.c

Library:

libmcolib.a

mco_db_extend_dev_tRT

Prototype

Arguments

Description

Return Codes

Example

Files

mco_db_extend_dev_t
RT