How to load cache group?

Question

Dear ChrisJenkins,
My project has a timesten . There is a table (using read only cache group) in timesten.
ex :
create table A as (id number, content varchar(20));
insert into A values (1, 'a1');
insert into A values (2, 'a2');
insert into A values (n, 'an');
commit;
The table (A) loaded 10 rows ('a1' --> 'a10'). if I execute the sql following :
"Load cache group A where id >=2 and id <=11"
, how will the timesten execute the sql above ?
I suggest :
the timesten don't load rows (id=2-->10) because the memory has the rows ,
the timesten only load rows (id=11) because the memory don't has the row
Is it true ?
Thanks,rgds
TuanTA

Answer 1

In your example you are using a regular table not a readonly cache group table. If you are using a readonly cache group then the table would be created like this:
CREATE READONLY CACHE GROUP CG_A
AUTOREFRESH MODE INCREMENTAL INTERVAL 10 SECONDS STATE PAUSED
FROM
ORACLEOWNER.A ( ID NUMBER, CONTENT VARCHAR(20));
This assumes that the table ORACLEOWNER.A already exists in Oracle with the same schema. The table in TimesTen will start off empty. ALso, you cannot insert, delete or update the rows in this table directly in TimesTen (that is why it is called a READONLY caceh group); if you try you will get an error. All data for this table has to originate in Oracle. Let's say that in Oracle you now do the following:
insert into A values (1, 'a1');
insert into A values (2, 'a2');
insert into A values (10, 'a10');
commit;
Stilll the table in TimesTen is empty. We can load the table with the data from Oracle using:
LOAD CACHE GROUP CG_A COMMIT EVERY 256 ROWS;
Mow the table in TimesTen had the same rows as the table in Oracle. Also, the LOAD operation changes the AUTOREFRESH state from PAUSED to ON. You still cannot directly insert/update and delete to this table in TimesTen but any data changes arising due to DML executed on the Oracle table will be captured and propagates to TimesTen by the AUTOREFRESH mechanism. If you now did, in Oracle:
UPDATE A SET CONTENT = 'NEW' WHERE ID = 3;
INSERT INTO A VALUES (11, 'a11');
COMMIT;
Then, after the next autorefresh cycle (every 10 seconds in this example), the table in TimesTen would contain:
1, 'a1'
2, 'a2'
3, 'NEW'
4, 'a4'
5, 'a5'
6, 'a6'
7, 'a7'
8, 'a8'
9, 'a9'
10, 'a10'
11, 'a11'
So, your question cannot apply for READONLY cache groups...
If you used a USERMANAGED cache group then your question could apply (as long as the cache group was not using AUTOREFRESH and the table had not been marked READONLY). In that case a LOAD CACHE GROUP cpmmand will only load qualifying rows that do not already exist in the cache table in TimesTen. If rows with the same primary key exist in Oracle they are not loaded, even if the other columns have different values to those in TimesTen. Contrast this with REFRESH CACHE GROUP which will replace all matching rows in TimesTen with the rows from Oracle.
Chris