Help in Delete operation

Question

I have a problem when deleting rows from a table. When I created the database the following delete statement worked fine, but now it takes a lot to complete. To delete 600 rows it takes more than 10 minutes. Maybe the transaction log is full, but i don't know how to check the space assigned to it or where is it.
The delete operation is the following one.
DELETE FROM event_TTT WHERE event_TTT.event_id IN
(SELECT event.event_id FROM event WHERE event_TTT.event_id=event.event_id and event.MM_id=1328)

Answer 1

Thank you for your information about statistics. After reading some papers and after checking that automatic statistics are being gathered in my system, I think that my tables do not fulfill the requirements to gather statistics manually ("statistics on tables which are significantly modified during the day"). Maybe I'm wrong. I'll continue reading about this.
Anyway, I've new data about my delete operation. I think it is very slow, but I'll give you the details:
DELETE FROM event_track e
WHERE EXISTS
SELECT
NULL
FROM event e1
WHERE e1.event_id = e.event_id
AND e1.pdep_mission_id = 1328
AND ROWNUM = 1
The is an index on e1.pdep_mission_id.
e1.event_id and e.event_id are primary keys.
Number of rows on e = 117000.
Number of rows on e1 = 120000
Number or rows to delete = 3500
This is the execution plan (with autotrace):
Plan hash value: 660928614
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | DELETE STATEMENT | | 1 | 254 | 217K (1)| 00:31:20 |
| 1 | DELETE | EVENT_TRACK | | | | |
|* 2 | FILTER | | | | | |
| 3 | TABLE ACCESS FULL | EVENT_TRACK | 119K| 28M| 667 (3)| 00:00:06 |
|* 4 | COUNT STOPKEY | | | | | |
|* 5 | TABLE ACCESS BY INDEX ROWID| EVENT | 1 | 9 | 2 (0)| 00:00:01 |
|* 6 | INDEX UNIQUE SCAN | PK_EVENT271 | 1 | | 1 (0)| 00:00:01 |
Predicate Information (identified by operation id):
2 - filter( EXISTS (SELECT 0 FROM "PDEP"."EVENT" "E1" WHERE ROWNUM=1 AND
"E1"."EVENT_ID"=:B1 AND "E1"."PDEP_MISSION_ID"=1305))
4 - filter(ROWNUM=1)
5 - filter("E1"."PDEP_MISSION_ID"=1305)
6 - access("E1"."EVENT_ID"=:B1)
Estadísticas
11207 recursive calls
26273 db block gets
24517966 consistent gets
23721872 physical reads
4316076 redo size
932 bytes sent via SQL*Net to client
1105 bytes received via SQL*Net from client
6 SQL*Net roundtrips to/from client
12 sorts (memory)
0 sorts (disk)
3518 rows processed
This operation took 2 hours and 5 minutes to complete the deletion of 3500 rows. Do I have to assume that this is correct or maybe I'm doing something wrong ??
Thank you in advance.