Sync Error - 6004 JSON parser invalid start of JSON. < : 0

[LanaJewell]

Hi there, 

We operate several maps in AGOL with layers from enterprise geodatabases and hosted feature services. Within the past few days, field users started reporting that their maps couldn't sync and the sync error read as " < : 0 " repeated several times. Upon examining the errors and logs further, we parsed out the full error as "Job error 6004 JSON parser invalid start of JSON. < : 0". This error only appears on layers linked to an enterprise geodatabase, not any of the other hosted feature services, and the error for surveyors repeated once for every layer linked to an enterprise GDB. We made no major changes to the GDBs within the past week. These maps have all been running successfully for various lengths of time, up to 1 year. The enterprise GDBs are version 10.4.1 and 10.8.1 .

Does anyone know how to resolve this error?

[VenkataKondepati · Accepted solution]

A few quick points you can check:

Server logs → On the ArcGIS Server hosting those enterprise GDB services, look at the verbose logs around the time of sync. They usually show the first service/layer returning invalid JSON.

Service health → Restart the service and validate its data store connection. Sometimes the connection to the enterprise geodatabase goes stale, especially with older 10.4.x/10.8.x releases.

Upgrade / patching → There are known JSON parser bugs in earlier releases that were patched in later 10.8.x / 10.9. If you can, apply the latest patches for your ArcGIS Server and geodatabase versions.

Test isolation → Publish a test feature service from the same enterprise GDB. If that service syncs fine, the issue may be data-specific (bad characters, null geometries, or corrupt attachments).

Attachments / domains → Corrupted attachments or invalid coded domain values often cause sync to fail with JSON errors. Run CheckGeometry and validate domains on the problem layers.

 If this is blocking field users, a practical workaround is to disable sync on the failing layers (temporarily remove them from maps) or republish the enterprise service until you can patch.

[LanaJewell]

All excellent advice. It turned out to be a setting that my company IT had changed in reference to our enterprise geodatabases, so we were able to have them reverse the change, but we used the server logs to determine the specific errors/layers and that this was likely in relation to the service health or a JSON parser bug they had attempted to patch. This did not end up being data-specific/layer-specific or surveyor-specific.

Thanks for all of your suggestions! 

[CodyPatterson]

Hey @LanaJewell 

I'm suspicious of a possible AGOL side change that may have caused this to happen. It may be due to the large version difference that comes from 10.4.1 and 10.8.1 GDBs. From the Enterprise support matrix, 10.4.1 is considered in retirement, but 10.8.1 is considered mature, so a case can still be made. Would it be possible to consider opening a case with ESRI support or possibly upgrading Enterprise?

Cody

[LanaJewell]

Hi Cody, to be clear they are separate maps operating separate layers out of two different enterprise GDBs (one is the 10.4.1 and the other is the 10.8.1) but all the maps are throwing the same error. There isn't any crossover between the two GDBs on the AGOL side so I wouldn't expect the version difference to throw an error. Good to know that our 10.4.1 is out of date and due for an upgrade!