Limit the size of data with time windows

After you assign a calendar, you can create time windows by using the ifx_TSDW_createWindow() routine. A time window consists of one or more adjacent virtual partitions. You can create multiple time windows. Time windows cannot overlap each other.

A time window is identified by a begin virtual partition and an end virtual partition. The begin virtual partition is the first virtual partition that is included in the time window, while the end virtual partition is the first virtual partition that is excluded from the time window. For example, if you want to compare the data of the first 3 months of the year for 2010, 2011, and 2012, you can create three time windows: January through March for each year, each of which contains three virtual partitions, by running the following statements:

ifx_TSDW_createWindow('demo_dwa', 'demo_mart', 'informix', 'ts_data_v', 0, 3); 
ifx_TSDW_createWindow('demo_dwa', 'demo_mart', 'informix', 'ts_data_v', 12, 15); 
ifx_TSDW_createWindow('demo_dwa', 'demo_mart', 'informix', 'ts_data_v', 24, 27);

Or by using time stamps to identify the virtual partitions:

ifx_TSDW_createWindow('demo_dwa', 'demo_mart', 'informix', 'ts_data_v',
	'2010-01'::datetime year to month, '2010-04'::datetime year to month);
ifx_TSDW_createWindow('demo_dwa', 'demo_mart', 'informix', 'ts_data_v',
	'2011-01'::datetime year to month, '2011-04'::datetime year to month);
ifx_TSDW_createWindow('demo_dwa', 'demo_mart', 'informix', 'ts_data_v',
	'2012-01'::datetime year to month, '2012-04'::datetime year to month);

This figure shows three time windows that each contain three virtual partitions:

To remove a time window and the time series data it contains from the accelerator, use the ifx_TSDW_dropWindow() routine. The time window to be dropped is identified by the virtual partition it starts with. For example, if you want to remove the time window for January to March 2010, run the following statement:

ifx_TSDW_dropWindow('demo_dwa', 'demo_mart', 'informix', 'ts_data_v', 0);

Or by using a time stamp to identify the time window:

ifx_TSDW_dropWindow('demo_dwa', 'demo_mart', 'informix', 'ts_data_v',
	'2010-01'::datetime year to month);

This figure shows two time windows that each contain three virtual partitions.

You can remove time windows when the data mart is in LoadPending or Active state. When you remove a time window in an Active data mart, the time series data for the time window is removed from the data mart immediately.

For example, you can move the time windows so that you can query on the second 3 months of the years 2011 and 2012 by running the following statement:

ifx_TSDW_moveWindows('demo_dwa', 'demo_mart', 'informix', 'ts_data_v');

That is equivalent to:

ifx_TSDW_moveWindows('demo_dwa', 'demo_mart', 'informix', 'ts_data_v', 1);

This figure shows that two time windows are moved forward in time by one time interval: