Oracle 12.1.0.2: Export failed with ORA-20002: Version of statistics table "MYSTATSTAB" is too old. Please try upgrading it with dbms_stats.upgrade_stat_table

I am trying to follow these steps in 12.1.0.2 and it fails when I run the step 3 (export stats).  This works well in 11g.  

BEGIN

dbms_stats.Create_stat_table(user, 'MY_STATS_TAB');

END;

exec dbms_stats.upgrade_stat_table(user, 'MY_STATS_TAB')

BEGIN

   DBMS_STATS.Export_table_stats (USER,

                                  stattab   => 'MY_STATS_TAB',

                                  tabname   => 'MD_TABLE_INFO',

                                  statid    => '11g_stats');

END;

ORA-20002: Version of statistics table "wwfuser"."MY_STATS_TAB" is too old.  Please try upgrading it with dbms_stats.upgrade_stat_table

ORA-06512: at "SYS.DBMS_STATS", line 18000

ORA-06512: at line 2

On further research we found that this issue occurs when database NLS_LENGTH_SEMANTICS are set to CHAR. By default we have CHAR settings in place of BYTE.

This is oracle bug 18459892 that fixed in 12.2.

After changing NLS_LENGTH_SEMANTICS it worked fine.

exec dbms_stats.drop_stat_table(ownname => 'WWFUSER', stattab => 'MY_STATS_TAB');

ALTER SESSION SET NLS_LENGTH_SEMANTICS = BYTE

exec dbms_stats.create_stat_table(ownname => 'WWFUSER', stattab => 'MY_STATS_TAB');

EXEC dbms_stats.export_table_stats(ownname => 'WWFUSER',tabname => 'MD_TABLE_INFO',stattab => 'MY_STATS_TAB',statid => 'Q21212');

Another alternative is to create stats table in SYS schema or with BYTE character set.

by SYS user:

EXEC dbms_stats.create_stat_table(ownname => 'SYS',stattab => 'STATTAB',tblspace => 'WWFDATA'); 

grant all on STATTAB TO wwfmgr;

then by wwf user:

EXEC dbms_stats.export_table_stats(ownname => 'WWFUSER',tabname => 'MD_TABLE_INFO',stattab => 'STATTAB',statid => 'Q21212',statown => 'SYS');

 Hope it helps.