I am new to Oracle, and I am not quite understanding the size calculations shown in OEM under tablespaces. I know it should be simple and my well be.
I need to monitor the table space but not sure what I am looking at. Should I go after the "Available Space Used(%)" or the "Allocated Space Used(%)" to monitor?
If I am running a script to alert when a threshold is met, which % should I use?
"Allocated Space Used(%)" reports the utilization of a tablespace based on the current size of its datafiles. Typically the value of this metric is close to 100% which causes a lot of false positive alerts.
Go after "Available Space Used(%)". That reports the utilization of a tablespace based on the configured maximum size of its datafiles (and the available free space in the filesystem or ASM diskgroup).
Example:
Tablespace TS1 consist of a single datafile that is 10 GB and contains 10 GB data. The datafile is configured as autoextensible with a maximum size of 20 GB. The single datafile of TS1 is on a filesystem with more than 10 GB free space.
"Allocated Space Used(%)" - 100%
"Available Space Used(%)" - 50%
If the single datafile of TS1 is in a filesystem with only 5 GB free space:
"Allocated Space Used(%)" - 100%
"Available Space Used(%)" - 66.6%
