During migration from repository 2 to 3, the migration process scans all content in repositories for artifact paths to migrate. As artifacts are migrated, a special token unique per repo and migration run, is stored in the artifact attribute file. The token intended purpose was to help a subsequent run of the migration process, reusing the migrationagent database, to know what files have already been migrated to repository 3.
However it has been well established since original design of the migration process that subsequent runs of the migration process is NOT SUPPORTED any longer, without a complete migration reset, which includes deleting the repository 2 migrationagent database. Since the migrationagent database stores this unique token, the token will be lost and make the attribute stored and read from artifact attributes file not effective any longer.
During testing, removing the storing and reading of this token attribute improves migration wall clock time by a noticeable degree - in some tests as much as 30%.
If safe to do, remove the storing and reading of this attribute during migration.