How to resolve ** mach_vm_map (size = 8388608) failed (error code = 3) *** error: cannot highlight region error

HI in my application I am downloading files from server and the total file size is over 9GB. After uploading 1 GB the data application crashes and shows an error as ** mach_vm_map (size = 8388608) failed (error code = 3) * ** error: cannot allocate region. Can anyone help me to solve this problem.

+(void)base64Decode:(NSData *)fData writeToFile:(NSFileHandle *)fHandle
{
    unsigned char inBuffer[4] ;
    unsigned char outBuffer[3] ;

    NSRange part ;
    part.location = 0 ;
    part.length = 1 ;

    NSMutableData *oData = [[NSMutableData alloc] init] ;
    BOOL bInProgress = YES ;
    int i ;
    int total = 0 ;

    while ( bInProgress )
    {
        inBuffer[0] = inBuffer[1] = inBuffer[2] = inBuffer[3] = 0 ;
        outBuffer[0] = outBuffer[1] = outBuffer[2] = 0 ;

        for ( i = 0 ; i < 4 ;  )
        {
            if ( [fData length] > part.location )
            {
                [fData getBytes:inBuffer+i range:part] ;
                part.location++ ;
                if ( ( inBuffer[i] == 0x0d ) || ( inBuffer[i] == 0x0a ) )
                    continue ;
                else
                    i++ ;
            }
            else
            {
                bInProgress = NO ;
                break ;
            }
        }

        //      if ( i != 4 )
        //      {
        //          NSLog ( @"Less\n" ) ;
        //      }

        int unexpect = 0 ;

        for ( int j = 0 ; j < i ; j++ )
        {
            if ( ( inBuffer[j] >= 'A' ) && ( inBuffer[j] <= 'Z' ) )
            {
                inBuffer[j] -= 'A' ;
            }
            else
            {
                if ( ( inBuffer[j] >= 'a' ) && ( inBuffer[j] <= 'z' ) )
                {
                    inBuffer[j] -= 'a' ;
                    inBuffer[j] += 26 ;
                }
                else
                {
                    if ( ( inBuffer[j] >= '0' ) && ( inBuffer[j] <= '9' ) )
                    {
                        inBuffer[j] -= '0' ;
                        inBuffer[j] += 52 ;
                    }
                    else
                    {
                        if ( inBuffer[j] == '+' )
                        {
                            inBuffer[j] = 62 ;
                        }
                        else
                        {
                            if ( inBuffer[j] == '/' )
                            {
                                inBuffer[j] = 63 ;
                            }
                            else
                            {
#ifdef DEBUG
                                NSLog ( @"fHandle Unexpected char: %c: %x\n", inBuffer[j], inBuffer[j] ) ;
#endif
                                unexpect++ ;
                            }
                        }
                    }
                }

            }

        }

        i -= unexpect ;

        int len = (i * 6) / 8 ;

        if ( ( i * 6 ) % 8 )
            len++ ;

        total += len ;

        outBuffer[0] = ( inBuffer[0] << 2 ) | ( ( inBuffer[1] & 0x30 ) >> 4 );
        outBuffer[1] = ( ( inBuffer[1] & 0x0f ) << 4 ) | ( ( inBuffer[2] & 0x3c ) >> 2 );
        outBuffer[2] = ( ( inBuffer[2] & 0x03 ) << 6 ) | ( ( inBuffer[3] & 0x3f ) );

        [oData appendBytes:outBuffer length:len] ;

        if([oData length] > 1024*10)
        {

            NSError *error;


        BOOL dataWritten=[self writeData:oData toFileHandle:fHandle error:&error];

            NSLog(@"dataWritten %hhd",dataWritten);

            if(oData)
            {
                [oData release];
                oData = nil ;
            }

            //[oData release];
            oData = [[NSMutableData alloc] init] ;
        }

    }
    //fwrite([oData bytes], 1, [oData length], fHandle) ;
    //[fHandle writeData:oData] ;

      NSError *error;

    [self writeData:oData toFileHandle:fHandle error:&error];



    if(oData)
    {
        [oData release];
        oData = nil ;
    }   //  NSLog ( @"Total written: %d\n", total ) ;
}






+(BOOL)writeData:(NSData *)data
     toFileHandle:(NSFileHandle *)fileHandler
            error:(NSError **)error
{
    @try
    {
        [fileHandler writeData:data];
    }
    @catch (NSException *e)
    {
        if (error != NULL)
        {
            NSDictionary *userInfo = @{
                                       NSLocalizedDescriptionKey : @"Failed to write data",
                                       // Other stuff?
                                       };
            *error = [NSError errorWithDomain:@"MyStuff" code:123 userInfo:userInfo];
        }
        return NO;
    }
    return YES;
}



Here fileHandler is NSFileHandle *pdfPathHandle = [NSFileHandle fileHandleForWritingAtPath:filePath];