If you have your SYSTEM tablespaces with a high percentage you can do the following to purge OPTSTAT_SNAPSHOT$/I_ OPTSTAT_SNAPSHOT$
SQL> select SEGMENT_NAME, segment_type, bytes/(1024*1024) SIZE_MB from
dba_segments where owner = 'SYS' and segment_name like '%OPTSTAT_SNAPSHOT%';
SEGMENT_NAME SEGMENT_TYPE SIZE_MB
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OPTSTAT_SNAPSHOT$ TABLE 8905
I_OPTSTAT_SNAPSHOT$ INDEX 7827
SQL> execute dbms_stats.purge_stats (DBMS_STATS.PURGE_ALL);
SQL> select SEGMENT_NAME, segment_type, bytes/(1024*1024) SIZE_MB from
dba_segments where owner = 'SYS' and segment_name like '%OPTSTAT_SNAPSHOT%';
SEGMENT_NAME SEGMENT_TYPE SIZE_MB
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OPTSTAT_SNAPSHOT$ TABLE 0.25
I_OPTSTAT_SNAPSHOT$ INDEX 0.0625