When the schema/user doesn't have an entry in dba_ts_quotas

Question

DB version:11.2.0.2
Developers have been creating/dropping objects in LANTS_ENTMT_NA_DEV_01 schema for several weeks now. Today, while trying to create a table in this schema they got
ORA-01536: space quota exceeded for tablespace 'LANTS_DATA'So, I wanted to check the quota allocated to this user. But this user doesn't have an entry in dba_ts_quotas ! This means that this user was never granted any quota on any tablespace . Right ?
But, I am curious , without any QUOTA , how this user was able to create objects in its default tablespace until now and suddenly get "ORA-01536: space quota exceeded" error today.
SQL > select distinct tablespace_name from dba_segments where owner = 'LANTS_ENTMT_NA_DEV_01';
TABLESPACE_NAME
LANTS_DATA
SQL > select MAX_BYTES from dba_ts_quotas where username = 'LANTS_ENTMT_NA_DEV_01';
no rows selected
SQL > select username, default_tablespace from dba_users where username = 'LANTS_ENTMT_NA_DEV_01';
USERNAME                       DEFAULT_TABLESPACE
LANTS_ENTMT_NA_DEV_01          LANTS_DATA
SQL > select count(*) from dba_ts_quotas where username = 'LANTS_ENTMT_NA_DEV_01';
  COUNT(*)
         0
SQL > alter user LANTS_ENTMT_NA_DEV_01 quota 20g on LANTS_DATA;
User altered.
-- After setting the quota, the user has an entry in dba_ts_quotas
SQL > select MAX_BYTES from dba_ts_quotas where username = 'LANTS_ENTMT_NA_DEV_01';
MAX_BYTES
2.1475E+10
SQL > select TABLESPACE_NAME, MAX_BYTES/1024/1024/1024 from dba_ts_quotas where username = 'LANTS_ENTMT_NA_DEV_01';
TABLESPACE_NAME                          MAX_BYTES/1024/1024/1024
LANTS_DATA                                                     20If LANTS_ENTMT_NA_DEV_01 didn't have any quota at all on this tablespace , this user should have got a different error ie. "ORA-01950: no privileges on tablespace" as shown in the test below.
SQL> create user testuser02 identified by abcd123 default tablespace FRCRS_TS;
User created.
SQL> grant create session to testuser02;
Grant succeeded.
SQL> grant select on dba_objects to testuser02;
Grant succeeded.
SQL> grant create table, create session to testuser02;
Grant succeeded.
SQL> select count(*) from dba_ts_quotas where username= 'TESTUSER02';
  COUNT(*)
         0
SQL> conn testuser02/abcd123
Connected.
SQL> create table john as select * from dba_objects where rownum < 30;
create table john as select * from dba_objects where rownum < 30
ERROR at line 1:
ORA-01950: no privileges on tablespace 'FRCRS_TS'

Answer 1

So, I wanted to check the quota allocated to this user. But this user doesn't have an entry in dba_ts_quotas ! This means that this user was never granted any quota on any tablespace . Right ?no, this means that this user currently doesnt have quota, but it could have in the past
But, I am curious , without any QUOTA , how this user was able to create objects in its default tablespace until now and suddenly get "ORA-01536: space quota exceeded" error today.see above, or:
users with the UNLIMITED TABLESPACE system privilege have unlimited quota on all tablespaces without giving any specific quota on a tablespace