Customer is using OEM ETL to get the Usage on the tablespaces, but it is too high for them.
This is because the ETL gets the Tablespace size in bytes and the Tablespace used in bytes.
But the value on Tablespace size in bytes is the CURRENT size of the tablespace.
From OEM there are some values:
bytes: This is the current size of the Tablespace.
maxbytes: This is the maximum Tablespace Size if all the datafile reach their max size.
So, customer is interested in getting:
Maximum Tablespace Size and
MAX_TS_PCT_USED: This is the percent of MAX_TS_SIZE reached and is the most important value in the query, as this reflects the true usage before DBA intervention is required.
For instance, you can see that on autoextensible tablespaces the MAX size can be much bigger.