ERROR 002555: The ArcGIS Data Store (relational) is in read-only mode and new items cannot be published. Please check available disk space

Error Message

Attempts to publish new items to Portal for ArcGIS from ArcGIS Pro or ArcMap fail, and return the following error message in the ArcGIS Server logs:

Error:   
ERROR 002555: The ArcGIS Data Store (relational) is in read-only mode and new items cannot be published. Please check available disk space.

Additionally, attempts to add items in Portal for ArcGIS fail, and return the following error message:

Error:   
The ArcGIS Data Store (relational) is in read-only mode and new items cannot be published.

Cause

The relational data store is automatically placed in the read-only mode if the disk space is less than 1024 MB.

Solution or Workaround

1. Increase the disk space of the ArcGIS Data Store machine. For more information refer to ArcGIS Enterprise: Disk space requirements.
2. Change the relational data store from read-only to read-write mode. Refer to the solution section of this article, Error: Failed to create new feature(s). General Function Failure [database error has occured.] for more information.