What does the SyncOnce tag mean?

I have a Python toolbox and this xml document was created.


<?xml version="1.0" encoding="UTF-8"?>
<metadata xml:lang="en">

or is there a list of what all tags mean or information about the xml structure?

I know there are other tags that can go in this document like a summary tag which can be accessed/edited through the Item Description. However there is no edit section for SyncOnce.


It's just something ArcGIS uses to maintain and track changes to metadata. Nothing you need to set yourself.

According to some old docs [1] and [2]

When metadata is created, the following elements are added to the ESRI section, which is used by ArcCatalog to maintain metadata:

  • Esri/MetaID — Metadata ID (ESRI Profile)
  • Esri/CreaDate — Creation Date (ESRI Profile)
  • Esri/CreaTime — Creation Time (ESRI Profile)
  • Esri/SyncOnce — Synchronize Once (ESRI Profile)

The Metadata ID element is intended to provide a unique identifier for each metadata record. Its value is a globally unique identifier (GUID) that is generated by the computer.

The Creation Date and Time are the date and time when the metadata document was created by ArcCatalog or initialized programmatically. These values will never change. All dates and times that are written to the metadata by ArcCatalog are recorded in formats that adhere to the FGDC standard. Dates are written in yyyymmdd format.Times are the local time and are written in HHMMSSSS format.

The value of the Synchronize Once element will initially be "TRUE". The value "TRUE" indicates that while metadata has been created, synchronization hasn't yet taken place.


Upon synchronization, SyncOnce is replaced with SyncDate and SyncTime. Automatic updates and other editing operations in the User Interface, or programmatically updates through the IXmlPropertySetEdit::SetProperty , will add ModDate and ModTime.

Anytime ArcGIS creates metadata, automatic or not, these ESRI elements will be added.

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