Home » RDBMS Server » Performance Tuning » Dictionary_cache = 0 ?
Dictionary_cache = 0 ? [message #298042] Mon, 04 February 2008 14:23 Go to next message
DrNeko
Messages: 17
Registered: January 2007
Location: NJ
Junior Member
Hello,
I'm running Oracle 10.2g on a Windows 2000 Server. I've set the SGA to Automatic Shared Memory Management. However, I've noticed that in the shared pool, the dictionary_cache is always 0. I've increases the SGA to shrink no less than 400MB, and the dictionary_cache is still 0. Sometimes the shared pool grows to 600MB, and the dictionary_cache doesn't change. Is there a way I can increase the dictionary_cache? Thanks.
Re: Dictionary_cache = 0 ? [message #298043 is a reply to message #298042] Mon, 04 February 2008 14:43 Go to previous messageGo to next message
Michel Cadot
Messages: 64139
Registered: March 2007
Location: Nanterre, France, http://...
Senior Member
Account Moderator
There is no parameter dictionary cache.
Do you mean buffer cache?
It is always 0 if you don't set it and use sga_target.
This does not mean there is no buffer cache but that it is dynamically set.
Check V$SGA_DYNAMIC_COMPONENTS

Regards
Michel

[Updated on: Mon, 04 February 2008 14:45]

Report message to a moderator

Re: Dictionary_cache = 0 ? [message #298299 is a reply to message #298043] Tue, 05 February 2008 10:52 Go to previous messageGo to next message
DrNeko
Messages: 17
Registered: January 2007
Location: NJ
Junior Member
I was referring to the dictionary cache itself. I haven't seen it being used, even before I enabled Automatic Shared Memory Management. I've queried V$SGA_DYNAMIC_COMPONENTS, and here's the result.
shared pool                                                      662700032                              654311424                              0                                      0                                      194                                    GROW           IMMEDIATE      2/5/2008 10:30:10 AM 8388608                                
large pool                                                       58720256                               41943040                               0                                      0                                      351                                    GROW           IMMEDIATE      2/5/2008 10:54:52 AM 8388608                                
java pool                                                        8388608                                8388608                                0                                      0                                      0                                      STATIC                                             8388608                                
streams pool                                                     50331648                               50331648                               0                                      50331648                               0                                      STATIC                                             8388608                                
DEFAULT buffer cache                                             318767104                              268435456                              0                                      0                                      545                                    SHRINK         IMMEDIATE      2/5/2008 10:54:52 AM 8388608                                
KEEP buffer cache                                                0                                      0                                      0                                      0                                      0                                      STATIC                                             8388608                                
RECYCLE buffer cache                                             0                                      0                                      0                                      0                                      0                                      STATIC                                             8388608                                
DEFAULT 2K buffer cache                                          0                                      0                                      0                                      0                                      0                                      STATIC                                             8388608                                
DEFAULT 4K buffer cache                                          0                                      0                                      0                                      0                                      0                                      STATIC                                             8388608                                
DEFAULT 8K buffer cache                                          0                                      0                                      0                                      0                                      0                                      STATIC                                             8388608                                
DEFAULT 16K buffer cache                                         0                                      0                                      0                                      0                                      0                                      STATIC                                             8388608                                
DEFAULT 32K buffer cache                                         0                                      0                                      0                                      0                                      0                                      STATIC                                             8388608                                
ASM Buffer Cache                                                 0                                      0                                      0                                      0                                      0                                      STATIC                                             8388608                                


I should point out that when I queried v$sgastat, it doesn't list the dictionary cache. This is the query I've used:
select name
from v$sgastat
where pool = 'shared pool'
and name like '%cache%'
order by name;

Array of cached attr       
library cache              
row cache                  
row cache child latch      
sim cache nbufs            
sim cache sizes
Re: Dictionary_cache = 0 ? [message #298316 is a reply to message #298299] Tue, 05 February 2008 11:59 Go to previous messageGo to next message
Michel Cadot
Messages: 64139
Registered: March 2007
Location: Nanterre, France, http://...
Senior Member
Account Moderator
"row cache" is the other name for dictionary cache.
It is historical because it is a cache that stores rows and not blocks like the other ones.

Regards
Michel
Re: Dictionary_cache = 0 ? [message #298336 is a reply to message #298316] Tue, 05 February 2008 14:35 Go to previous messageGo to next message
DrNeko
Messages: 17
Registered: January 2007
Location: NJ
Junior Member
Thanks for clearing that up for me. Is there any way I can increase the row cache or library cache aside from increasing the SGA/Shared Pool?
Re: Dictionary_cache = 0 ? [message #298337 is a reply to message #298336] Tue, 05 February 2008 15:13 Go to previous messageGo to next message
Michel Cadot
Messages: 64139
Registered: March 2007
Location: Nanterre, France, http://...
Senior Member
Account Moderator
No, shared pool is... shared, Oracle will take the space it needs depending on your activity.
Why do you want to increase this/these specific area/s?

Regards
Michel
Re: Dictionary_cache = 0 ? [message #298598 is a reply to message #298337] Wed, 06 February 2008 13:00 Go to previous messageGo to next message
DrNeko
Messages: 17
Registered: January 2007
Location: NJ
Junior Member
I was told that by increasing these areas help increase performance, providing that I have enough memory to spare.
Re: Dictionary_cache = 0 ? [message #298605 is a reply to message #298598] Wed, 06 February 2008 13:52 Go to previous messageGo to next message
Michel Cadot
Messages: 64139
Registered: March 2007
Location: Nanterre, France, http://...
Senior Member
Account Moderator
It can increase performances only if you have performances issues due to these areas otherwise it does nothing and might even decrease performances.
Don't shot in the dark you might kill your child instead of stopping a burglar.

Regards
Michel
Re: Dictionary_cache = 0 ? [message #298614 is a reply to message #298605] Wed, 06 February 2008 17:01 Go to previous message
DrNeko
Messages: 17
Registered: January 2007
Location: NJ
Junior Member
Thanks for the advice. Smile
Previous Topic: RBO to CBO migration
Next Topic: Index Entry
Goto Forum:
  


Current Time: Thu Dec 08 08:11:06 CST 2016

Total time taken to generate the page: 0.07906 seconds