ORA-01555 caused by SQL statement

Hello,

Oracle 11.2.0.4 SE

Got  recently above error followed by SQL Server statement. Ic hcecked all alert log file and found out two other such errors but from February with different SQL Statements.

Tue Dec 17 00:58:08 2019

ORA-01555 caused by SQL statement below (SQL ID: 23dxcadp10rm4, Query Duration=3445 sec, SCN: 0x0008.1f0ed741):

/* + NO_PARALLEL */select  * from (

SELECT ...

Any idea about severity of such error ? Should be followed up or can be ignored?

Thanks in advance for any help,