What are DD_HASHSIZE and DD_HASHMAX? How are they tuned?

Hi. The true is these couple of parameter are new for me. DD_HASHSIZE and DD_HASHMAX. I looked up the Administrator's and Performace guide for IDS 7.31 and i can't find anything about them. In the forum, I learned something but i think is not enough, so far I guess they allow tunning the dicctionary cache and these parameter I have to add into onconfig file. But, what are the correct values that they will have? How do I know if the server is correctly tunning? Could somebody explain them to me or where can I find a information. Thank a lot for your advices. -- Francisco Huezo Administrador de Base de Datos Ministerio de Hacienda Proyecto SAFI Cond. Tres Torres, T-2, N-8 San Salvador, El Salvador Tel. (503) 225-3700 ext 102 Cel: (503) 830-7469 ------------------------------------------------- Brainbench Certified Power Builder 6.0 Informix DBA Unix Administration ( General ) http://www.brainbench.com/transcript.jsp?pid=23525 -------------------------------------------------- Moving to Linux is more evolution than revolution.

I am a informix online dynamic workgroup server user .I wanted to know the formula for cost of query ,when we run a set explain on; on a query Regards, Pankaj K

Francisco Huezo wrote: > > Hi. > > The true is these couple of parameter are new for me. > DD_HASHSIZE and DD_HASHMAX. > I looked up the Administrator's and Performace guide for IDS 7.31 > and i can't find anything about them. > > In the forum, I learned something but i think is not enough, so far I guess > they allow tunning the dicctionary cache and these parameter I have to add into > onconfig file. Correct. They are mostly undocumented. See my chapter in the Informix Handbook for others. > But, what are the correct values that they will have? > How do I know if the server is correctly tunning? The value of DD_HASHSIZE must be a prime number and DD_HASHMAX a smallish integer. The former is the number of hash buckets the latter the number of slots in each bucket. The product of the two is the maximum number of tables the dictionary hash table will hold but hashing realities makes the actual count somewhat less. Someone posted a script that purports to approximate the tablename hash that the engine uses to assign tables to buckets so you can calculate a good DD_HASHMAX for a given DD_HASHSIZE and play with different values of the latter. Art S. Kagel > Could somebody explain them to me or where can I find a information. > > Thank a lot for your advices. > > -- > Francisco Huezo > Administrador de Base de Datos > Ministerio de Hacienda > Proyecto SAFI > Cond. Tres Torres, T-2, N-8 > San Salvador, El Salvador > Tel. (503) 225-3700 ext 102 > Cel: (503) 830-7469 > ------------------------------------------------- > Brainbench Certified > Power Builder 6.0 > Informix DBA > Unix Administration ( General ) > http://www.brainbench.com/transcript.jsp?pid=23525 > -------------------------------------------------- > Moving to Linux is more evolution than revolution.

Francisco Huezo wrote: > > Hi. > > The true is these couple of parameter are new for me. > DD_HASHSIZE and DD_HASHMAX. > I looked up the Administrator's and Performace guide for IDS 7.31 > and i can't find anything about them. > > In the forum, I learned something but i think is not enough, so far I guess > they allow tunning the dicctionary cache and these parameter I have to add into > onconfig file. Correct. They are mostly undocumented. See my chapter in the Informix Handbook for others. > But, what are the correct values that they will have? > How do I know if the server is correctly tunning? The value of DD_HASHSIZE must be a prime number and DD_HASHMAX a smallish integer. The former is the number of hash buckets the latter the number of slots in each bucket. The product of the two is the maximum number of tables the dictionary hash table will hold but hashing realities makes the actual count somewhat less. Someone posted a script that purports to approximate the tablename hash that the engine uses to assign tables to buckets so you can calculate a good DD_HASHMAX for a given DD_HASHSIZE and play with different values of the latter. Art S. Kagel > Could somebody explain them to me or where can I find a information. > > Thank a lot for your advices. > > -- > Francisco Huezo > Administrador de Base de Datos > Ministerio de Hacienda > Proyecto SAFI > Cond. Tres Torres, T-2, N-8 > San Salvador, El Salvador > Tel. (503) 225-3700 ext 102 > Cel: (503) 830-7469 > ------------------------------------------------- > Brainbench Certified > Power Builder 6.0 > Informix DBA > Unix Administration ( General ) > http://www.brainbench.com/transcript.jsp?pid=23525 > -------------------------------------------------- > Moving to Linux is more evolution than revolution.