> For the complete documentation index, see [llms.txt](https://docs.verifone.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.verifone.com/support-us/verifone-hq/vhq-parameter-management/retaining-parameter-values-on-changing-software-assignment.md).
# Retaining parameter values on changing software assignment
Retain custom parameter values and carry forward parameter templates when software assignments change in VHQ across application upgrades and device hierarchy modifications.
Keywords
Also called: parameter carry forward, retain parameter values. Search terms: reference set change, application upgrade, parameter qualifiers.
## What is parameter value retention?
VHQ retains custom parameter values you've defined whenever the software assignment changes.
## When parameters are carried forward
Parameters can be carried forward or retained when a software assignment changes in the following scenarios:
* Reference set assignment is edited at hierarchy level.
* Reference set assignment is edited at device level (single or multiple).
* Reference set is edited at the reference set library.
* Reference set assignment is changed using device import XML.
* Reference set assignment is changed using external APIs.
* Reference set assignment changes without user intervention, such as:
* The device reports a different attribute that qualifies it for a different reference set.
* The device moves to a different hierarchy (via GUI, import, API, or IP/location change).
* Reference set configuration changes from *Direct Assignment* to *Inherit from Hierarchy*, or vice versa.
## When VHQ retains parameter values
VHQ retains parameter values when all of the following are true:
* An application name with a different version is being assigned.
* The current application/version combination has associated parameter definition files.
* The target application/version combination has associated parameter definition files.
* Parameter values are user-defined for the current application/version combination.
VHQ also supports carrying forward parameters assigned as parameter templates.
{% hint style="info" %}
**Example**: App 1.0 has PT1 (instances m1, m2, m3 with values 5, 6, 7) assigned. The user unassigns App 1.0 and assigns App 2.0, which contains PT1 (instances m3, m4, m2 with values 8, 9, 4). With carry-forward, App 2.0's PT1 instances m3, m4, m2 are assigned values 5, 9, 4 instead of 8, 9, 4 — since m3 is common to both versions, its value (5) carries forward from the previous instance.
{% endhint %}
## Carry-forward logic
When upgrading a device from application A version V1 to version V2 (via a new reference set or package assignment):
```xml
FOR (each parameter currently used by application A and version V1)
{
IF (given parameter is also available in VPDX file of application A and version V2)
{
Copy that parameter and value under given device for application A and version V2
}
IF (given parameter is NOT available in VPDX file of application A and version V2)
{
OMIT that parameter and value under given device for application A and version V2
}
}
FOR (each parameter that is defined in VPDX file of application A and version V2 and which is NOT defined in VPDX file of application A and version V1)
{
Insert this parameter for device under application A and version V2 with default value from VPDX file of application A and version V2
}
```
When the upgrade happens via XML import instead, the same carry-forward logic (Part 1) runs first:
```xml
FOR (each parameter currently used by application A and version V1)
{
IF (given parameter is also available in VPDX file of application A and version V2)
{
Copy that parameter and value under given device for application A and version V2
}
IF (given parameter is NOT available in VPDX file of application A and version V2)
{
OMIT that parameter and value under given device for application A and version V2
}
}
FOR (each parameter that is defined in VPDX file of application A and version V2 and which is NOT defined in VPDX file of application A and version V1)
{
Insert this parameter for device under application A and version V2 with default value from VPDX file of application A and version V2
}
```
Then (Part 2), if the XML import file specifies values for any of those parameters, VHQ applies those values afterward — overwriting any carried-forward or default value. Parameters in the XML that aren't defined in application A version V2's VPDX file can't be imported, and the import log records the error.
```xml
```
## Parameter qualifiers
The **Parameter Template** feature is enhanced so the **Qualifiers** widget is now labeled **Models** in the adding and editing parameter template screens.
Go to **Device Management** > **Applications Library** to add a parameter template:
Provide a **Parameter Template Name** and click **Models** to choose the models, then save.
Go to **Device Management** > **Applications Library** to edit a parameter template — select it, click the edit icon, click **Models**, and save.
---
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