Editing Common MySQL Problems with EPrints (section)

=== Resolution ===
To fix this issue you will need to manually modify the affected MySQL column.  In the example error message above, if we assume you updated the <code>maxlength</code> attribute for the <code>volume</code> field of the <code>eprint</code> data object from 6 to 9, you will need to manually run the following MySQL command to update the database to correspond with the EPrints configuration for this field:
 ALTER TABLE eprint MODIFY COLUMN volume VARCHAR(9) DEFAULT NULL;

Ideally running <code>epadmin update ARCHIVEID</code> would update fields to effect changes to attributes like <code>maxlength</code>.  Unfortunately, due to the extensive number or scenarios of how fields could be changed, implementing robust ways that will reliably modify MySQL columns, whilst ensuring data is not lost or worse tables becoming corrupted or inconsistent, is a very complex task.  However, writing a script to do a consistency check between the field configuration for EPrints data objects and the structure of these tables in the MySQL database for the archive [https://github.com/eprints/eprints3.4/issues/163 is being investigated].