Oracle DB Error: ORA-01555

[Anonymous]

I am importing data from Orcle BD using ODBC connecor. I didn't have any problem importing data from the same table before but now running into issues. The data is fairly large, more than million rows and about 25 columns. It starts out good but after several hours of import, I get below error: 

"Failed to save modifications to teh server. Error returned: ' OLD DB or ODBC error: [Datasource.error] Oracle: ORA-01555: snapshot too old: rollback segment number 76 with name" _SYSSMU76_1882479614$" too small".

I have no idea what this cryptic error means. I found this about ORA-01555 but don't understand it either. 

I can use DirectQuery without any issues but the DirectQuery is very very slow. 

Can somebody please help? 

Thanks, 

S.P

[dramus · Accepted solution]

That error is coming from the oracle database.

It is an issue with the length of time that your transaction has been open. Oracle is trying to preserve the read context (What the database looked like when you started the query), but the data it needs has aged out of the UNDO Tablespace.

You have two options:

1. Tune your query so that the data is returned quicker.
2. Talk to your DBA about increasing the size of the UNDO tablespace.

http://www.orafaq.com/wiki/ORA-01555

[Anonymous]

Thanks.. I will reduce the Query size and try it over the weekend. Hopefully, it will work. 

Is there a limit in Power BI on query time and table size? 

Thanks