create table dropme_t(f_plain, f_masked)
as select 'vah ','каждый новый select выдает рандомное значение' from dual;
Table created

BEGIN
 DBMS_REDACT.ADD_POLICY(
   object_schema   => null,
   object_name     => 'dropme_t',
   column_name     => 'f_masked',
   policy_name     => 'test_masking',
   function_type   => DBMS_REDACT.RANDOM,
   expression      => '1=1');
END;
/
PL/SQL procedure successfully completed

select * from redaction_policies;

OBJECT_OWNER         OBJECT_NAM POLICY_NAME  EXPRESSION ENABLE POLICY_DES
-------------------- ---------- ------------ ---------- ------ ----------
TESTUSER             DROPME_T   test_masking 1=1        YES    

insert into dropme_t values('Stax','в блоке какой-то мусор (битый блок)');
1 row inserted

select * from dropme_t;

F_PLAIN F_MASKED
------- -------------------------------------------------------------------------------
vah     F}d|k6aCN&l%s>iKV.t-{FqS^6|5$Ny[f>%=,VzcnF-E4^*kvN5M<f2s~V=UDn:{1^E]LvB$/fMeT~J
Stax    5kF&~cfb=sN.1knjE{V6/svrM$^>7{~zU,fF?$1#]4nNG,/+e<vVO473mD~^W<?;uL1f_DGC}T/ngLO

select * from dropme_t where f_masked like '%мусор%';

F_PLAIN F_MASKED
------- -------------------------------------------------------------------------------
Stax    >WK=uhDnF_SE}pLvNg[M&xT~VocU.!\1^wk]6)d/f se>1l7n({mF9t?v0$uNA|G~8,}VI%O1@4&;^Q-


begin
  dbms_redact.drop_policy(null,'dropme_t','test_masking');
end;
/
PL/SQL procedure successfully completed

select * from redaction_policies;

OBJECT_OWNER         OBJECT_NAM POLICY_NAME  EXPRESSION ENABLE POLICY_DES
-------------------- ---------- ------------ ---------- ------ ----------


select * from dropme_t;

F_PLAIN F_MASKED
------- -------------------------------------------------------------------------------
vah     каждый новый select выдает рандомное значение
Stax    в блоке какой-то мусор (битый блок)

drop table dropme_t purge;
Table dropped


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