Table of Contents
Billing Terminology
Storage Billing Modes
Storage Billing Modes determine how the billable storage quantity is calculated during a billing period.
Storage charges can be based on either:
- The number of actual Volumes stored.
- The number of storage slots used or allocated.
The selected mode determines whether billing uses accumulated daily quantities, the highest recorded quantity, or the lowest recorded quantity.
Storage Modes
| Mode | Meaning for Billing |
|---|---|
| Storage | The general billing category for Volumes held in a Repository during the billing period. The selected Storage Billing Mode determines how the billable quantity is calculated. |
| Daily Total | The sum of the actual inventory count recorded for each day. The resulting quantity is measured in Volume-days and is normally used for per-Volume, per-day billing. |
| Real High-Water | The highest number of actual Volumes stored at any point during the billing period. |
| Real Low-Water | The lowest number of actual Volumes stored at any point during the billing period. |
| Slot Total | The sum of the daily storage-slot counts. The resulting quantity is measured in slot-days and is used when the Customer is charged for storage capacity. |
| Slot High-Water | The highest number of storage slots used or allocated at any point during the billing period. |
| Slot Low-Water | The lowest number of storage slots used or allocated at any point during the billing period. |
Real and Slot Measurements
Real and Slot measurements use different methods to determine the billable storage quantity.
| Measurement Type | Counts | Typical Use |
|---|---|---|
| Real | Actual tape Volumes present in the Repository. | Billing the Customer for each physical Volume stored. |
| Slot | Storage positions occupied, allocated or required for the Customer's inventory. | Billing the Customer for storage capacity rather than individual Volumes. |
A Slot quantity may be different from the actual Volume inventory when:
- Some slots are empty but remain allocated to the Customer.
- Storage is sold in fixed blocks of slots.
- Inventory quantities are rounded up to the next storage-unit size.
- A container or storage position represents more than one Volume.
- The Customer reserves more capacity than is currently being used.
Daily Total Example
The following example shows the actual number of Volumes stored over five days.
| Day | Actual Volumes |
|---|---|
| 1 | 101 |
| 2 | 108 |
| 3 | 104 |
| 4 | 115 |
| 5 | 110 |
The Real Storage measurements are:
| Mode | Result |
|---|---|
| Daily Total | 538 Volume-days |
| Real High-Water | 115 Volumes |
| Real Low-Water | 101 Volumes |
If storage is charged at $0.01 per Volume per day, the Daily Total charge is:
538 × $0.01 = $5.38
Real High-Water Example
Real High-Water uses the highest actual Volume count recorded during the billing period.
From the previous example:
Real High-Water = 115 Volumes
If the High-Water quantity is applied to all five days:
115 × 5 days × $0.01 = $5.75
The Billing Rules must define whether the High-Water value is charged once or multiplied by the number of days in the billing period.
Real Low-Water Example
Real Low-Water uses the lowest actual Volume count recorded during the billing period.
From the previous example:
Real Low-Water = 101 Volumes
If the Low-Water quantity is applied to all five days:
101 × 5 days × $0.01 = $5.05
Real Low-Water may be used to:
- Apply a minimum storage charge.
- Identify the Customer's base storage usage.
- Compare minimum and maximum inventory levels.
- Support contract-specific storage calculations.
Slot Total Example
Assume storage is allocated in blocks of 10 slots. Each daily actual inventory count is rounded up to the next block of 10.
| Day | Actual Volumes | Billable Slots |
|---|---|---|
| 1 | 101 | 110 |
| 2 | 108 | 110 |
| 3 | 104 | 110 |
| 4 | 115 | 120 |
| 5 | 110 | 110 |
The Slot Storage measurements are:
| Mode | Result |
|---|---|
| Slot Total | 560 slot-days |
| Slot High-Water | 120 slots |
| Slot Low-Water | 110 slots |
If storage is charged at $0.01 per slot per day, the Slot Total charge is:
560 × $0.01 = $5.60
Slot High-Water Example
Slot High-Water uses the highest slot quantity recorded during the billing period.
From the previous example:
Slot High-Water = 120 slots
If the Slot High-Water quantity is applied to all five days:
120 × 5 days × $0.01 = $6.00
Slot High-Water may be used when the Customer is charged for the maximum storage capacity used during the billing period.
Slot Low-Water Example
Slot Low-Water uses the lowest slot quantity recorded during the billing period.
From the previous example:
Slot Low-Water = 110 slots
If the Slot Low-Water quantity is applied to all five days:
110 × 5 days × $0.01 = $5.50
Slot Low-Water may be used when the Customer is charged for a minimum level of allocated or reserved storage capacity.
Comparison
| Mode | Measurement | Result Type | Typical Billing Use |
|---|---|---|---|
| Daily Total | Sum of daily actual Volume counts. | Volume-days | Per-Volume, per-day storage billing. |
| Real High-Water | Highest actual inventory count. | Volumes | Maximum actual storage usage. |
| Real Low-Water | Lowest actual inventory count. | Volumes | Minimum actual storage usage. |
| Slot Total | Sum of daily slot quantities. | Slot-days | Per-slot, per-day capacity billing. |
| Slot High-Water | Highest slot quantity. | Slots | Maximum storage capacity used or allocated. |
| Slot Low-Water | Lowest slot quantity. | Slots | Minimum storage capacity used or allocated. |
Billing Rule Requirements
The Billing Rules should clearly define:
- Which Storage Billing Mode applies.
- Whether storage is measured using Volumes or slots.
- How often inventory is sampled.
- Whether slot quantities are occupied, allocated or rounded quantities.
- The size of any slot block or rounding unit.
- The price per Volume or slot.
- Whether the price is a daily or period rate.
- Whether High-Water and Low-Water quantities are charged once or multiplied by the number of days.
- Whether minimum charges or exclusions apply.
The meaning of a slot must be agreed in the Customer Billing Profile. Occupied slots, allocated slots and rounded storage capacity may produce different invoice totals.
Inventory
| Term | Description |
|---|---|
| Inventory | The number of items held at a particular point in time, usually the current inventory or the inventory recorded on a specified date. |
| Total inventory | The accumulated inventory across the billing period. For daily billing, this is normally the sum of each day’s inventory count and represents item-days rather than a single physical count. |
| Inventory high-water | The highest inventory count recorded at any point during the billing period. This can be used when billing the customer for their maximum storage usage. |
| Inventory low-water | The lowest inventory count recorded at any point during the billing period. This shows the minimum storage level and may be used for minimum-usage billing or analysis. |
Example
Suppose a customer’s inventory over five days is:
| Day | Inventory count |
|---|---|
| 1 | 100 |
| 2 | 110 |
| 3 | 105 |
| 4 | 120 |
| 5 | 115 |
On day 5, the Inventory is 115 Volumes.
Total Inventory, the sum of the number of Volumes over the 5 days, 550 Volume days. Billing on the total inventory number at 27.50
Inventory High-water, the highest Volume daily count, 120 Volumes. Billing off the high-water mark at 30.00
Inventory Low-water, the lowest Volume daily count, 105 Volumes. Inventory low-water mark is usually used to assess the minimum amount of storage a Customer uses over a certain time frame.
The important distinction is that inventory, high-water, and low-water are point-in-time counts, while total inventory usually accumulates counts across time.