Is possible to flush data from RAM to disk automatically ?

Question

hello all,
My question is regarding to flushing of Data from RAM to DISK .
question is whether any flag set is available at Berekeley DB to flush the Data from RAM to DISK automatically( on any criteria whenever the pages in cache become full or some thing else).
Context is based on CDS with memory pool not Transactional.
thanks
Rath.

Answer 1

hello Debsubhra Roy,
Thanks Debsubhra, thanks for your valuble comments.
Actually My objective is to periodically flush the in memory Data to physical database at Filesystem to minimize the write cycle of Flash.
based on your opinion, i have created a in memory Database in cache,and It is working fine with in cache memory, but problem is ,it is not flushing (exactly not creating) to a Physical file of "Database name" at the filesystem.
1.i checked with with below api 's for flushing,but not worked.
myEnvironment->memp_trickle(100,0);
                    myEnvironment->memp_sync(lsn);
                    mydbpDbHandle->sync(0);
2.Secondly my assumption is that ,whenever the Cache memory will fill,then it will flush the Data in to physical Database "TestDb" named at the Db->open () api.
it is also not working, it is showing exception of "cannot allocate space from Buffer cache " exception.
For better understanding i am pasting my sample code, please see that and give me a solution to reach my objective.
#include <iostream>
#include <db_cxx.h>
using namespace std;
typedef unsigned char byte;
struct DBKey
     int iSerNum;
struct DBValue
     int RolNo;
     int Marks;
DbLsn *lsn;
int icount=0;
class DBEnvironment{
protected:
     DbEnv* myEnvironment;
     int percent;
     int *nwrotep;
public:
     DBEnvironment(){}
     ~DBEnvironment(){}
     int ienvCreation()
          myEnvironment = new DbEnv(0);
          myEnvironment->set_flags(DB_DIRECT_DB,0);               
          myEnvironment->set_cachesize(0, 100*100, 1);     
          myEnvironment->set_shm_key(100);
          myEnvironment->open("/root/Desktop/TestD", DB_CREATE|DB_INIT_MPOOL|DB_THREAD|DB_INIT_CDB| DB_SYSTEM_MEM,0644);
int ienvClose()
          myEnvironment->close(0);
          delete myEnvironment;
          myEnvironment = NULL;
class Database :public DBEnvironment
private:
     Db* mydbpDbHandle;
     DbMpoolFile* myDbMpooFile;
public:
     Database(){}
     ~Database(){}
     int openDB()
          byte breturn=false;
          if(mydbpDbHandle == NULL )
               mydbpDbHandle = new Db(myEnvironment, 0);
               if(mydbpDbHandle->open(NULL,NULL,"TestDb", DB_BTREE, DB_CREATE|DB_THREAD,0644) ==0)
                    breturn = true;
     int closeDB()
          byte breturn = false;
          if(mydbpDbHandle != NULL)
               mydbpDbHandle->close(DB_NOSYNC);//     0     
               delete mydbpDbHandle;
               mydbpDbHandle = NULL;
               breturn = true;
int insertDB(const byte* cpkey, void* vpvalue)
          Dbt dbtkey;
          Dbt dbtvalue;
          Dbc* dbcp = NULL;
          DBKey mytkey;
          DBValue mytdata;
          byte breturn = false;
          icount++;
          int k;
          try
               if (mydbpDbHandle == NULL)
                    return(breturn);
               memset(&dbtkey, 0, sizeof(dbtkey));
               memset(&dbtvalue, 0, sizeof(dbtvalue));
               dbtkey.set_data((void*)cpkey);
               dbtkey.set_size(sizeof(mytkey));
               dbtvalue.set_data(vpvalue);
               dbtvalue.set_size(sizeof(mytdata));
               mydbpDbHandle->cursor(NULL, &dbcp, DB_WRITECURSOR);
               dbcp->put(&dbtkey, &dbtvalue,DB_KEYLAST);
               cerr<<"\n "<<icount<<"inserted";
     //flushing the Data ,whenever the icount reaches multiples of 10     
               k=(icount%10);
               if(k==0)
                    //myEnvironment->memp_trickle(100,0);
                    myEnvironment->memp_sync(lsn);
                    mydbpDbHandle->sync(0);
                    cerr<<"\n sync called to flush.";
               breturn = true;
          catch(DbException ex)
               cerr<<ex.what();
          if(dbcp!=NULL)
               dbcp->close();
               dbcp = NULL;
     return(breturn);
     int iserachRecord(const byte* cpkey, void* vpvalue)
          Dbt dbtkey;
          Dbt dbtvalue;
          Dbc* dbcp = NULL;
          DBKey mytkey;
          byte breturn = false;
          try
               if (mydbpDbHandle == NULL)
                    return(breturn);
               memset(&dbtkey, 0, sizeof(dbtkey));
               memset(&dbtvalue, 0, sizeof(dbtvalue));
               dbtkey.set_data((void*)cpkey);
               dbtkey.set_size(sizeof(mytkey));
               mydbpDbHandle->cursor(NULL, &dbcp, DB_READ_COMMITTED);
               if(dbcp->get(&dbtkey, &dbtvalue, DB_SET)!=DB_NOTFOUND)
                    cerr<<"\nRecord Found...";
                    memcpy(vpvalue,(byte *)dbtvalue.get_data(), dbtvalue.get_size());
                    breturn = true;
          catch(DbException ex)
               cerr<<ex.what();
          if(dbcp!=NULL)
               dbcp->close();
               dbcp = NULL;
          return(breturn);
int main()
     Database* Dbp=new Database();
     Dbp->ienvCreation();
     Dbp->openDB();
     DBKey Key,Key1,SearchKey;
     DBValue Value,Value1,RetrieveValue;
     for(int i=1;i<100;i++)
          Key.iSerNum=i;
          Value.RolNo=i+1;
          Value.Marks=i+2;
          Dbp->insertDB((byte*)&Key,(void*)&Value);
     cerr<<"\n------------Search Results-----------";
     SearchKey.iSerNum=10;
     Dbp->iserachRecord((byte*)&SearchKey,&RetrieveValue);
     cerr<<"\nkey is:- "<<SearchKey.iSerNum<<"\nvalue -RolNo:- "<<RetrieveValue.RolNo<<"\nMark:- "<<RetrieveValue.Marks;
//     Dbp->closeDB();
//     Dbp->ienvClose();
}