Essbase® Analytic Services Database Administrator's Guide | | Update Contents | Previous | Next | Print | ? | |
Information Map | |
This chapter explains how to calculate time series data in block storage databases. For example, you can do inventory tracking by calculating the first and last values for a specific time period. You can also calculate period-to-date values.
This chapter pertains to block storage databases. For block storage databases, time series calculations assume that you have Dynamic Time Series members defined in the outline. Dynamic Time Series members are not supported for aggregate storage database outlines. However, you can perform time series calculations and queries on aggregate storage databases using the MDX PeriodsToDate function. For more information, see the MDX section of the Technical Reference.
This chapter includes the following sections:
Using time balance and variance reporting tags on the dimension tagged as accounts, you can tell Analytic Services how to perform time balance calculations on accounts data.
Analytic Services usually calculates a parent in the dimension tagged as time by consolidating or calculating the formulas on the parent's children. However, you can use accounts tags, such as time balance and variance reporting tags, to consolidate a different kind of value. For example, if you tag a parent member in the accounts dimension with a time balance property of First, Analytic Services calculates the member by consolidating the value of the member's first child. For example, in the Sample Basic database, the Opening Inventory member in the Measures dimension (the accounts dimension) has a time balance property of First. This member represents the inventory at the beginning of the time period. If the time period is Qtr1, Opening Inventory represents the inventory available at the beginning of Jan (the first member in the Qtr1 branch).
To use accounts tags, you must have a dimension tagged as accounts and a dimension tagged as time. You use the First, Last, and Average tags (time balance properties) and the Expense tag (variance reporting property) only on members of a dimension tagged as accounts. The dimensions you tag as time and accounts can be either dense or sparse dimensions.
Note: If you are using Intelligent Calculation, changing accounts tags in the database outline does not cause Analytic Services to restructure the database. You may have to tell Analytic Services explicitly to recalculate the required data values. For a discussion of how and why to perform a recalculation, see Changing Formulas and Accounts Properties.
When you tag a dimension as accounts, Analytic Services knows that the dimension contains members with accounts tags. When you tag a dimension as time, Analytic Services knows that this dimension is the one on which to base the time periods for the accounts tags.
In the Sample Basic database, the Measures dimension is tagged as accounts, and the Year dimension is tagged as time.
Figure 193: Sample Basic Outline Showing Accounts and Time Tags
For information on tagging accounts and time dimensions, see Creating a Time Dimension and Creating an Accounts Dimension.
For an accounts dimension member, you can tell Analytic Services to move the last value for each time period up to the next level. To report the last value for each time period, set the member's time balance property as Last. (In the database outline, the TB Last tag is displayed.)
For example, in the Sample Basic database, the accounts member Ending Inventory consolidates the value for the last month in each quarter and uses that value for that month's parent. For example, the value for Qtr1 is the same as the value for Mar.
Figure 194: Sample Basic Outline Showing Last Tag
For information on tagging an accounts member as Last, see Setting Time Balance Properties.
By default, Analytic Services does not skip #MISSING or zero (0) values when calculating a parent value. You can choose to skip these values. For a discussion of how and why to skip #MISSING values, see Skipping #MISSING and Zero Values.
For an accounts dimension member, you can tell Analytic Services to move the first value for each time period up to the next level. To report the first value for each time period, set the member's time balance property as First. (The tag displays as TB First in the database outline.)
For example, in the Sample Basic database, the accounts member Opening Inventory consolidates the value of the first month in each quarter and uses that value for that month's parent. For example, the value for Qtr1 is the same as the value for Jan.
Figure 195: Sample Basic Outline Showing First Tag
For information on tagging an accounts member as First, see Setting Time Balance Properties.
By default, Analytic Services does not skip #MISSING or zero (0) values when calculating a parent value. You can choose to skip these values. For a discussion of how and why to skip #MISSING values, see Skipping #MISSING and Zero Values.
For an accounts dimension member, you can tell Analytic Services to average values across time periods and consolidate the average up to the next level. For example, you can tell Analytic Services to average the values for Jan, Feb, and Mar and then use that value for the Qtr1 value. To report the average value for each time period, set the member's time balance property as Average.
For information on tagging an accounts member as Average, see Setting Time Balance Properties.
By default, Analytic Services does not skip #MISSING or zero (0) values when it calculates a parent value. Thus, when it calculates the average, Analytic Services aggregates the child values and divides by the number of children, regardless of whether the children have #MISSING or zero values. You can tell Analytic Services to skip #MISSING and zero values. For a discussion of how and why to skip #MISSING values, see Skipping #MISSING and Zero Values.
You can tell Analytic Services how to treat #MISSING and zero (0) values when doing time balance calculations. A #MISSING value is a marker in Analytic Services that indicates that the data in this location does not exist, does not contain any meaningful value, or was never entered.
By default, Analytic Services does not skip #MISSING or 0 (zero) values when calculating a parent value.
You can override this default by setting a skip property. For a discussion of how skip properties work, see Setting Skip Properties.
For example, if you tag an accounts dimension member as Last and Skip Missing, then Analytic Services consolidates the last non-missing child to the parent. Consider the following example:
Accounts -> Time |
Jan |
Feb |
Mar |
Qtr1 |
---|---|---|---|---|
Tagging an account as Average and Skip Missing may produce different results from tagging that account as Average and Skip None. A calculation performed with Average and Skip None produces correct results because no data is skipped. But because grandparents with children are consolidated by summing the averages, results of a calculation on an account with Average and Skip Missing is incorrect unless you use Dynamic Calc or Two Pass tags.
The following table shows how Analytic Services consolidates the time dimension based on the time balance (TB) First, Last, and Average tags on accounts dimension members.
Accounts -> Time |
Jan |
Feb |
Mar |
Qtr1 |
|
---|---|---|---|---|---|
If you place a member formula on a time or accounts dimension, it may be overwritten by a time balance calculation.
Consider the following example from Sample Basic, in which Opening Inventory is tagged as First:
Measures -> Year |
Jan |
Feb |
Mar |
Qtr1 |
---|---|---|---|---|
Because Opening Inventory is tagged as First, Analytic Services calculates Opening Inventory for Qtr1 by taking the Opening Inventory for Jan value. Any member formula that is placed on Qtr1 in the database outline is overwritten by this time balance calculation.
You can calculate period-to-date values for data. For example, you can calculate the sales values for the current quarter up to the current month. If the current month is May, using a standard calendar quarter, the quarter total is the total of the values for April and May.
In Analytic Services, you can calculate period-to-date values in two ways:
This section explains how to use Dynamic Time Series members to dynamically calculate period-to-date values. Using Dynamic Time Series members is the most efficient method in almost all cases. For an example using the @PTD function to calculate period-to-date values, see Calculating Period-to-Date Values.
In order to calculate period-to-date values dynamically, you need to use a Dynamic Time Series member for a period on the dimension tagged as time. See Specifying Accounts and Time Dimensions.
You do not create the Dynamic Time Series member directly in the database outline. Instead, you enable a predefined Dynamic Time Series member and associate it with an appropriate generation number. This procedure creates a Dynamic Time Series member for you.
For example, if you want to calculate quarter-to-date values, you enable the Q-T-D member and associate it with the generation to which you want to apply the Dynamic Time Series member. In Sample Basic, the generation containing quarters is generation number 2, which contains the Qtr1, Qtr2, Qtr3, and Qtr4 members. Analytic Services creates a Dynamic Time Series member called Q-T-D and associates it with generation 2. The Q-T-D member calculates monthly values up to the current month in the quarter. For a brief discussion, see Enabling Dynamic Time Series Members.
Figure 196: Sample Basic Outline Showing Time Dimension
Dynamic Time Series members are not displayed as members in the database outline. Instead, Analytic Services lists the currently active Dynamic Time Series members in a comment on the time dimension. In the following outline, H-T-D (history-to-date) and Q-T-D (quarter-to-date) are active. H-T-D is associated with generation 1; Q-T-D is associated with generation 2.
Figure 197: Sample Basic Outline Showing Dynamic Time Series
Analytic Services provides eight predefined Dynamic Time Series members:
History-to-date |
These eight members provide up to eight levels of period-to-date reporting. How many members you use and which members you use depends on the data and the database outline.
For example, if the database contains hourly, daily, weekly, monthly, quarterly, and yearly data, you might want to report day-to date (D-T-D), week-to-date (W-T-D), month-to-date (M-T-D), quarter-to-date (Q-T-D), and year-to-date (Y-T-D) information.
If the database contains monthly data for the past 5 years, you might want to report year-to-date (Y-T-D) and history-to-date (H-T-D) information, up to a specific year.
If the database tracks data for seasonal time periods, you might want to report period-to-date (P-T-D) or season-to-date (S-T-D) information.
You can associate a Dynamic Time Series member with any generation in the time dimension except the highest generation number, irrespective of the data. For example, if you choose, you can use the P-T-D member to report quarter-to-date information. You cannot associate Dynamic Time Series members with level 0 members of the time dimension.
Note: We recommend you avoid assigning time balance properties (First, Last, Average, Skip Missing) to members set for dynamic calculations if you plan to use these members in Dynamic Time Series calculations. Doing so may retrieve incorrect values for the parent members in your accounts dimension.
To use Dynamic Time Series members, you need to enable them. If required, you can specify aliases for Dynamic Time Series members. For a brief discussion, see Specifying Alias Names for Dynamic Time Series Members.
To enable Dynamic Time Series members, see "Enabling Dynamic Time Series Members" in the Essbase Administration Services Online Help.
Note: The number of generations displayed depends on the number of generations in the time dimension. You cannot associate Dynamic Time Series members with the highest generation (level 0 members).
After you enable Dynamic Time Series members in the database outline, Analytic Services adds a comment to the dimension tagged as time. Figure 198 shows the Sample Basic database with H-T-D and Q-T-D defined.
Figure 198: Sample Basic Outline Showing Dynamic Time Series Members
Year Time (Active Dynamic Time Series Members: H-T-D, Q-T-D) (Dynamic Calc)
To disable a Dynamic Time Series member, tell Analytic Services not to use the predefined member.
To disable Dynamic Time Series members, see "Disabling Dynamic Time Series Members" in the Essbase Administration Services Online Help.
You can specify alias names for predefined Dynamic Time Series members, such as QtrToDate, for the Q-T-D Dynamic Time Series member. You can then use the alias names to retrieve the Dynamic Time Series members in Spreadsheet Services, Spreadsheet Add-in, or in a report.
You can create up to eight alias names for each Dynamic Time Series member. Analytic Services saves each alias name in the Dynamic Time Series alias table that you specify.
To create aliases for Dynamic Time Series members, see "Creating Aliases for Dynamic Time Series Members" in the Essbase Administration Services Online Help.
For information on specifying and displaying alias names, see Setting Aliases.
When you enable a Dynamic Time Series member and associate it with a generation number, Analytic Services creates a predefined generation name for that generation number. For information on creating generation names, see Naming Generations and Levels.
To display generation and level names, see "Naming Generations and Levels" in the Essbase Administration Services Online Help.
The following table shows the Dynamic Time Series members and their corresponding generation names:
Member |
Generation Name |
Member |
Generation Name |
---|---|---|---|
These member and generation names are reserved for use by Analytic Services. If you use one of these generation names to create a generation name on the time dimension, Analytic Services automatically creates and enables the corresponding Dynamic Time Series member for you.
For example, in Sample Basic, you can create a generation name called Quarter for generation number 2. Quarter contains quarterly data in the members Qtr1, Qtr2, and so on. When you create the generation name Quarter, Analytic Services creates and enables a Dynamic Time Series member called Q-T-D.
When you retrieve a Dynamic Time Series member, you need to tell Analytic Services the time period up to which you want to calculate the period-to-date value. This time period is known as the latest time period and must be a level 0 member on the time dimension.
Use the following methods to specify the latest time period:
The member-specific setting-for example, Q-T-D(May)-takes precedence over the <LATEST or Latest Time Series option setting.
The following example shows Sample Basic data. Q-T-D(May) displays the period-to-date value for May that is obtained by adding the values for Apr and May (8644 + 8929 = 17573).
Figure 199: Spreadsheet Showing Period-To-Date Value for May
If Dynamic Time Series members are part of the shared area between databases, define the Dynamic Time Series members in both databases, just as you would for regular members. For example, if the partition definition includes Qtr1, Qtr2, Qtr3, Qtr4, and the Dynamic Time Series member Q-T-D, define the Q-T-D member in both the source database and the target database.
If a Dynamic Time Series member is not part of the shared area between databases, Analytic Services gets the data for that member from the source database. You do not need to define the Dynamic Time Series member in both databases. However, this configuration is generally less efficient than including the Dynamic Time Series member in the partition definition.
For a comprehensive discussion of partitioning, see Creating and Maintaining Partitions.
![]() |