> For the complete documentation index, see [llms.txt](https://docs.os.uk/os-downloads/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.os.uk/os-downloads/products/addresses-and-names-portfolio/addressbase-plus-islands/addressbase-plus-islands-technical-specification/supply-and-update.md).
# Supply and update
AddressBase Plus Islands will be supplied as non-geographic chunks only. This is a way of dividing up the data into chunks that are supplied in separate volumes, which have a fixed maximum amount of records. The supply is not supplied with any reference to the geographic position of records.
Customers are able to take the AddressBase Plus Islands product as a Full Supply or Change Only Update (COU) supply.
## **Unzipped files**
The filename will be constructed as follows:
*productName\_supply\_ccyy-mm-dd\_vvv.format*
Where:
* **ProductName** is `AddressBasePlus_ISL`.
* **supply** is defined as `FULL` or `COU`.
* **ccyy-mm-dd** is the date the file was generated.
* **vvv** is the volume number of the file.
* **format** is the format of the files received, for example, `csv` or `gml`.
For example:
* `AddressBasePlus_ISL_FULL_2013-05-28_001.gml` (GML full supply)
* `AddressBasePlus_ISL_COU_2013-05-28_001.csv` (CSV COU supply)
## **Zipped files**
If the data has been provided in a ZIP file, the filename will be constructed as follows:
*productName\_supply\_ccyy-mm-dd\_vvv\_format.zip*
For example:
* `AddressBasePlus_ISL_FULL_2013-05-28_001_gml.zip` (GML full supply zipped)
## COU supply
AddressBase Plus Islands is available as a Full or Change Only Update supply.
A change-only update (COU) supply of data contains records or files that have changed between product refresh cycles. The primary benefit in supplying data in this way is that data volumes are smaller therefore reducing the amount of data that requires processing when compared to a full supply.
COU data enables a user to identify three types of change:
1. Deletes (CHANGE\_TYPE ‘D’) are objects that have ceased to exist in your area of interest since the last product refresh.
2. Inserts (CHANGE\_TYPE ‘I’) are objects that have been newly inserted into your area of interest since the last product refresh.
3. Updates (CHANGE\_TYPE ‘U’) are objects that have been updated in your area of interest since the last product refresh.
### Archiving
When users are Deleting, Inserting or Updating features it is up to the user to consider their archiving requirements. If deleted records are important to your business requirements you must take appropriate action to archive previous records.
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