A few of things to try

• Make sure feature caching is turned OFF
• Make sure that "Stop at breakpoints" is turned OFF
• Try increasing bulk read size in the advanced reader parameters
• Disable any further processing from the reader to check read performance alone
• Check for messages in the FME log, especially about memory optimization

Thanks @david_r​ 

The configuration to test is really simple and I've applied also some of the configuration suggested (i.e. increasing bulk read size).

Unfortunately nothing change in the performance. I also tried to unload the security agent in case FME stores some cache (not the feature one that is disabled) in a protected disk area. Same results.

I now try to do something at Oracle level like to re-create the table and reindexing it.

Because this blocking issue seems to be limited to this feature.

It is slow also for other tables but not as this one.

I will update the post as soon as tests completed.

Roberto

On the Oracle side, also check the entry for this table in USER_SDO_GEOM_METADATA. Are the values in DIMINFO consistent with your spatial data? Is the SRID value correct?