When altering an existing column by changing the field type or the field length, data loss can occur if the field has duplicate storage aliases. On an affected version, the logic that safeguards against data loss fails to account for data in fields that are aliases of the field being modified. The following workflow illustrates the issue:

  1. The user accesses a field on a table that is configured as an extension of another table (Table per Hierarchy).
  2. The user then alters the field by changing either its Type or its Length.
  3. The execution logic tests for data loss in that table only (not the entire hierarchy for the field).

Because the test does not detect any data in other tables that are also extensions of that same base table, the workflow continues to execute, causing data loss for that field in the other tables.

Steps to Reproduce

ServiceNow does not recommend any attempt on the part of the customer to reproduce the issue. If you have made a change to a field definition and have experienced data loss, please escalate to the ServiceNow support team for their assistance with an investigation.

ServiceNow is executing a maintenance change that will add a logical test to the workflow to cleanly abort when the risk of data loss is present. You may see one of the errors below when attempting to execute the workflow after the guardrail is in place:

  • Element is using storage alias. Cannot modify this element's type because it shares a storage alias. _alias_
  • Element is using storage alias. Cannot shrink this element's length because it shares a storage alias. _alias_
  • Update aborted because duplicate storage aliases defined for element [_name_._element_]


A workaround is not available at this time, but the issue is fixed in the available product releases listed in the Fixed In section below.

Related Problem: PRB674257

Seen In

Eureka Patch 1 Hot Fix 2
Geneva Patch 1
Geneva Patch 3 Hot Fix 2
Geneva Patch 4
Geneva Patch 5
Geneva Patch 6
Geneva Patch 6 Hot Fix 2
Geneva Patch 7
Geneva Patch 7 Hot Fix 1
Geneva Patch 9
Helsinki Patch 0 Hot Fix 1
Helsinki Patch 3
Helsinki Patch 4
Helsinki Patch 5

Fixed In

Geneva Patch 6 Hot Fix 2
Geneva Patch 7
Geneva Patch 8
Helsinki Patch 1
Helsinki Patch 2

Safe Harbor Statement

This "Planned Fixed In" information is intended to outline ServiceNow's general product direction and should not be included in making a purchasing decision. The information provided here is for information purposes only and may not be incorporated into any contract. It is not a commitment, promise, or legal obligation to deliver any material, code, or functionality. The development, release, and timing of any features or functionality described for our products remains at ServiceNow's sole discretion.

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Article Information

Last Updated:2017-11-07 11:37:07