[b]ORA-01450: maximum key length exceeded[/b]

Question

Hi I get this error when trying to migrate MS Access 2000 to Oracle. I get this error on foreign key and primary keys saying that the maximum key length has been exceeded.
What does this mean and how can I fix it? Can anyone help?
Thanks
Ray

Answer 1

Maximum key length also depends on tablespace block size. It seems that your value (1942) may be for 2K blocks.
At least for my 10.2.0.1.0 on Windoze it takes
1478 for 2k tablespace
3118 for 4k tablespace
6398 for 8k tablespace
If you have 2K blocks I'd say it is somewhat rather small blocks, I'd normally use 8K blocks.
So if you have possibility (have at least version 9, probably 9.2 don't know exactly) to create tablespaces with non default blocksize then as a temporal solution you can create tablespace with larger blocksize and create index in it.
Of course so you have to allocate also some memory for these blocksizes and so divide your memory in possibly less utilized pieces.
See example for my 8k default blocksize test DB:
SQL> create table v (a varchar2(4000), b varchar2(4000), c varchar2(4000));
Table created.
SQL> insert into v values (lpad('a', 4000, 'a'), null, null);
1 row created.
SQL> create index vidx on v (a, b, c);
create index vidx on v (a, b, c)
ERROR at line 1:
ORA-01450: maximum key length (6398) exceeded
SQL> alter system set db_16k_cache_size = 10240;
System altered.
SQL> create tablespace big datafile 'big.dbf' size 10 m blocksize 16k;
Tablespace created.
SQL> create index vidx on v (a, b, c) tablespace big;
Index created.
Gints Plivna
http://www.gplivna.eu
Message was edited by:
gintsp
Of course inserting a row was completely unnecessary :)