This would mean somebody on your system did an element export/import. The RTE you see means that importing the element takes a long time (more than 15 minutes). If this RTE remains there it would mean the import is blocked.
Reasons why it can take a long time: a lot of performance or alarm information that needs to be imported. Or the element config is rather large.
If this RTE would remain, it will be necesarry to analyze a dump of the SLDataMiner process.