SQL> alter session set "_optimizer_cost_model"=abc; ERROR: ORA-00096 (See ORA-00096.ora-code.com): invalid value ABC for parameter _optimizer_cost_model, must be from among choose, io, cpu
thanks amit * Christian Antognini wrote:
>Hi Peter > > > >>in 10.1.0.3 I tried to delete system statistics with >> >>exec DBMS_STATS.DELETE_SYSTEM_STATS; >> >> > >Notice that system statistics are always available in 10g. In fact even = >if you don't gather them, Oracle automatically gathers them with the = >NOWORKLOAD method. > > > >>No error. In sys.aux_stats$ the 'Flag' goes from 1 to 0.=20 >>And values for mreadtim,sreadtim.. stay set. (And I cannot=20 >>set them to NULL with SET_SYSTEM_STATS).=20 >> >> > >I never saw another behaviour. > > > >>Any idea how to convince the optimizer not to use the deleted = >> >> >statistics? > >For test purposes, i.e. to see what happen if they are not available, I = >run the following statements... > >delete aux_stats$; >commit; >shutdown immediate >startup >select * from aux_stats$; > >I know, I know, it's probably not the best approach, but I tested it = >many times on different databases and I never had problems... Notice = >that when the database is restarted a set of NOWORKLOAD statistics are = >gathered (to do so they read some blocks from each datafile): >- CPUSPEEDNW =3D ??? (depends on the CPU) >- IOSEEKTIM =3D 10=20 >- IOTFRSPEED =3D 4096 > >My guess, which is practically certitude, is that IOSEEKTIM/IOTFRSPEED = >are fix. > > >HTH >Chris >-- >http://www.freelists.org/webpage/oracle-l > > >
