# mco_db_extend_t
RT

Extend database memory within a transaction.

### Prototype

        MCO_RET	mco_db_extend_t(	/*IN*/ mco_trans_h  t,
                      /*IN*/ void * mem,
                      /*IN*/ uint4 size);

### Arguments

t | The current transaction handle
mem | The starting address of a block of memory
size | The size, in bytes, of the block of memory

### Description

> This function extends the amount of memory used by the database. Note that whereas `mco_db_extend()` must be called outside any transaction, `mco_db_extend_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

        const char * dbname = "SimpleDb";

        int main(int argc, char* argv[])
        {
            mco_db_h db;
            MCO_RET rc;
            char *mem = malloc( DBSIZE );

            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
                char	* mem2 = malloc(SECOND_SEGSZ);
                if( mem2 )
                {
                    rc =  mco_trans_start(db, MCO_READ_WRITE, MCO_TRANS_FOREGROUND, &t);
                    rc = mco_db_extend_t(t, mem2, SECOND_SEGSZ);

                    if ( MCO_S_OK != rc )
                        mco_trans_rollback();
                    else
                        mco_trans_commit();
                    ...
                }
            }
        }

### Files

Header file:
mco.h
Source file:
mcodb.c
Library:
libmcolib.a