Inventory Items

The Items tab is where an Inventory node’s stock is defined. Each item is one part number, with an opening quantity, a home zone, and a replenishment policy that tops it up on its own. Add items one at a time, or use Import Items to bring in a list.

What an item holds

Field	What it sets
Name (SKU)	The name logic refers to when it takes or stores this item
Zone	Which zone’s access time applies to a withdrawal
Quantity	Opening stock at the start of the run
Capacity	The most the item can hold. Blank for no limit
Unit Cost	Charged to the entity for each unit it takes
Unit Time	Handling time per unit, in minutes

Replenishment

Leave these blank and the item never reorders. Fill them in and the inventory keeps itself stocked.

Field	What it sets
Reorder Level	The stock level that triggers an order
Reorder Qty	How much to order, or the level to order up to
Reorder Policy	Fixed Quantity orders the same amount every time. Order Up To (s, S) orders however much is needed to reach the figure above
Max Outstanding Orders	How many orders may be in flight at once
Lead Time and Lead Time Unit	The delay from placing an order to the stock arriving
Holding Cost	A carrying charge per unit per hour of stock held
Ordering Cost	A fixed charge each time an order is placed

The trigger compares stock on hand plus stock already on order against the reorder level, so a slow supplier does not cause the same order to be placed over and over while the first is still in transit.

Reorder Level and Reorder Qty accept an expression, and it is worked out once at the start of each replication. That makes a variable a good master knob: put v_ReorderPoint on every item and a scenario can move the whole store at once. Entity attributes are not allowed, because no entity is involved when a reorder fires. Lead Time is different: it is sampled fresh for every order, so a distribution there gives genuine supplier variability.

Infinite Supply

Tick Infinite Supply and the item never runs out. It is the right answer for something you do not want to model the supply of: packaging tape, fasteners, water.

Be aware that infinite supply silently switches off the whole replenishment block. Reorder level, reorder quantity, policy, outstanding orders, lead time, and ordering cost are all still editable and all have no effect, with no warning. The one exception is the start of a run: an infinite item that starts at or below its reorder level, with both reorder fields filled, still places one order. If you want reorder behavior, leave it unticked and give the item a real quantity.

Capacity

An item’s effective ceiling is the lower of its own Capacity and the inventory’s total capacity. A plain STORE puts in what fits and sets a result code (stored, overflow or full). A STORE with WAIT waits until the whole amount fits, and asking it for more than that ceiling stops the run with a clear error rather than waiting forever, so a failed store shows up as a message rather than as a model that hangs.

Cost and time

Unit Cost is charged to the entity that takes the stock, added to its running total in no value classification (see Costs in a model). Holding Cost and Ordering Cost are reported against the inventory itself.

Unit Time is the handling time per unit, in minutes, and it must be a plain number. It is added to the zone’s access time to give the total time a withdrawal takes.

Importing and exporting items

Below the list, Import Items brings in a list of items, and Export appears once there is at least one item.

Import Items opens Import Inventory Items. Choose From File and Browse for a .csv, .xlsx, .xls or .tsv file, or choose Paste Rows and paste rows copied from a spreadsheet, then Parse Pasted Rows. The first row must be a header row. An Excel file is read from its first sheet, or from a sheet with “item” in its name.

Column Mapping pairs each item field with a column of your data. Name (SKU) is required: with no Name column the window asks you to pick the column that holds the item name. Name and Quantity show a warning mark while they are not mapped. The Preview shows the first 20 rows, and the Summary counts the items parsed, rows skipped and duplicate names found.

Import Mode is Add to existing items or Replace all items. When adding, and a name is already in the list, Duplicate handling is Skip duplicates (keep existing), Update existing with imported values or Import as new (rename duplicates). If an Excel file has a sheet named Zones, a box also offers to import its zones.

Export opens a menu: Export as CSV, Export as Excel, and Download Template, a file with only the column headings. The file lands beside a saved model, with a notice saying where; a model not yet saved asks where to put it.

Inventory Zones: access times by area of the store
Inventory Substitutions: what to take when an item is out
Inventory statements: STORE, TAKE, and REQUEST