Buffer Cache Size Consume Full SGA_target
Jun 14, 2013
If sga Buffer Cache Size consume full of SGA_target size, if possible that it will cause performance any issue. I am facing CPU 100% consuming while single query execute, Which query generate monthly report data.
I have two question
1)How to fix the CPU 100% consuming
2)How to find total number user hit oracle specific schema.
Oracle 10.2.0.5 Standard
Sga_target : 14G
Sga_max :20G
Pga :3G
Below SGA details
NAME BYTES/1024/1024
-------------------------------- ---------------
Fixed SGA Size 2.01795197
Redo Buffers 13.9804688
Buffer Cache Size 13632
Shared Pool Size 640
Large Pool Size 16
Java Pool Size 16
Streams Pool Size 16
Granule Size 16
Maximum SGA Size 20480
Startup overhead in Shared Pool 208
Free SGA Memory Available 6144
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Jul 30, 2012
Does cache buffer chain latch and buffer busy wait event are related to one any another.
Latch definition from Google says : Latches are simple, low-level serialization mechanisms to protect shared data structures in the system global area (SGA).
what does it mean my protect. Does this mean protects from aging as per LRU algorithm and getting removed from SGA
or
protect from other processes ,say from example from simultaneously DML operations.
or
both
Does buffer busy wait event occurs , because of the cache buffer chain latch ?
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Feb 22, 2013
how can we check the size of data buffer cache.
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May 20, 2013
what will be best buffer cache hit ratio for a database for good performance
note : in general
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Apr 18, 2012
I want to know what exact process happens in oracle architecture when an update query is fired.
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Mar 26, 2012
give a script to find how much my db buffe cache and redo log buffer cache is used and how much is free.
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Mar 3, 2011
Database : 9.2.0.7
Os : windows 2003 sevrer standdard edition
RAM 4 Gigs
The buffer cache hit ratio in this server is around 83%, where it normaly was around 98% before i did some maintenance activities.
I have done some maintenance activities in January on this database.
Maintenance activties includes below steps
1.In production i have deleted old data in the production tables
2.Reorganized tablespaces,tables
3.Rebuild indexes for those tables.
4. At last collected statistics for those tables.
Now after this activity the buffer cache hit ratio is very low.
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Nov 30, 2012
Considering the below factors, I am planning to increase the buffer cache value from 256Mb to 512Mb.
1. Buffer cache hit ratio value is around 35% even in the normal period.
2. free buffer requested value is below during peak & normal hours below.
Statistic Total per Second per Trans
--------------------------------- ------------------ -------------- ------------
free buffer requested 54,694,995 15,226.9 2,523.7
free buffer requested 23,412,674 6,501.7 2,585.9
3. most of the top 5 physical reads & logical reads queries are well tuned and some of queries are doing FTS on small tables (table count min 1500 max 35000). SO indexing option is not required for these queires. But these queries getting executed frequently.
SQL> show sga
Total System Global Area 2148534928 bytes
Fixed Size 731792 bytes
Variable Size 1879048192 bytes
Database Buffers 268435456 bytes
Redo Buffers 319488 bytes
5.top 5 waitevents during db slow performance & high cpu utilization (>80%) issue.
Top 5 Timed Events
~~~~~~~~~~~~~~~~~~ % Total
Event Waits Time (s) Ela Time
-------------------------------------------- ------------ ----------- --------
latch free 1,848,898 153,793 52.00
buffer busy waits 395,280 87,201 29.49
db file scattered read 3,488,648 34,199 11.56
enqueue 4,052 10,897 3.68
CPU time 5,567 1.88
6. Top 5 waitvents during normal activities and CPU utilization is around 40%.
Top 5 Timed Events
~~~~~~~~~~~~~~~~~~ % Total
Event Waits Time (s) Ela Time
-------------------------------------------- ------------ ----------- --------
CPU time 1,860 45.32
db file scattered read 1,133,669 985 23.99
imm op 776 605 14.73
sbtinfo2 208 139 3.40
sbtbackup 2 123 3.00
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Sep 27, 2010
1) Is shutting down the DB flush all the data buffers, from the buffer Cache?
2) In any oracle version, do we have any way to flush only the buffer Cache.
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Aug 19, 2010
1)If i issue a DELETE statement to delete a row, will this statement drag any data from the datafile to database buffer? How is the change made by a DELETE statement recorded in buffer cache? How is this change then applied to the data in datafiles after commit?
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Mar 28, 2011
How can i know which objects used keep buffer cache?
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Jan 15, 2011
I have some confusion about Keep Pool in Buffer Cache.
1. What is the reasoning for placing a table in the KEEP buffer pool because if it is frequently accessed, it will be around when needed (ie if it is constantly being accessed it will not age out) .
2. Would the table be still in the Default Pool if the Keep Pool is not sized and the command is being issued alter TABLE SCOTT.EMP storage (buffer_pool keep) ?
3. If the database is restarted will the table be wiped out of the Keep Pool and again be pinned to the Keep Pool ?
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Apr 25, 2013
I want to simulate latch : cache buffer chains wait event due to use of nested loop join for lookup tables
This is what a tried :
-- create parent / child tables
SQL>drop table emp1 purge;
drop table dept1 purge;
create table dept1 (dept_id number primary key,
dept_name char(30));
[Code]....
I traced many queries like the one given below (dept_id between 1 and n where n varied from 10 to 1000) but they always result in hash join
1* select d.dept_name, e.id from sys.dept1 d, sys.emp1 e where d.dept_id = e.dept_id and e.dept_id < 1000
Execution Plan
----------------------------------------------------------
Plan hash value: 619452140
----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 998K| 41M| 680 (2)| 00:00:09 |
|* 1 | HASH JOIN | | 998K| 41M| 680 (2)| 00:00:09 |
|* 2 | TABLE ACCESS FULL| DEPT1 | 999 | 34965 | 4 (0)| 00:00:01 |
|* 3 | TABLE ACCESS FULL| EMP1 | 999K| 8780K| 672 (2)| 00:00:09 |
----------------------------------------------------------------------------
what can I do to get a nested loop join to simulate latch : cache buffer chains?
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Jan 26, 2011
Say Database Buffer Cache configured as 2M and my updates may use 4m size,will it throw an error message or update will happen perfectly without any issues?
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May 7, 2011
I am currently in the favorable situation in which I have excess amounts of memory available on the database server - a single node setup. The server only serves the single instance and no other processing. Database size is around 2.3tb and memory is 50gb. For the majority of processing, AIX is allocating a significant amount (anywhere from 30-40%) of the memory to the AIX file system cache (persistent pages).
I've been trying to find documentation about this, but have not had any luck yet. My guess is that it would be better to allow Oracle to cache this data - meaning increase the SGA target and max size to allow for a larger buffer cache. However, the nice thing about the AIX cache is if process memory is needed, the file system cache gives up pages. If the memory was allocated to the SGA, its pretty much locked in.
I have read several articles stating that a larger buffer cache is not always better, as a larger cache takes more management. But having both of the caches active seem to be a waste of memory, effectively storing the data twice - once in AIX persistent pages and a second time in Oracle database buffer cache.
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Oct 3, 2010
Is there any relationship b/w tuning BUFFER CACHE and BUFFER BUSY WAITS?
1) Buffer Busy Waits are happening as the User process found the same Datablock is being used by another user in the BUFFER CACHE.
2) And also happens, when the server process found the same Datablock are being used in the Datafile.
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May 30, 2013
I have a serious doubt in oracle architecture functionality, when a user issues a update statement the data blocks are carried to db buffer cache and where does the changes to the data blocks are made???? Does a copy of the data block is kept in db buffer cache and the changes are made to the block in buffer cache?? or the a copy of the data block is kept in undo tablespace and changes are made to the blocks in the undo tablespace???
In simple the changes to the data blocks are made at db buffer cache or undo tablespace?
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Apr 30, 2013
What is By Default Buffer size in Oracle ......?
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Oct 5, 2010
In Oracle 9i
I know that db_block_size defines the standard/default block size for my datafiles.
I know db_cache_size defines the size of the my default database buffer of the size of my standard/default block size.
db_block_size = 8192 (8k)
db_cache_size = 200Mo of 8k block
Is there any needs for the other buffer cache
db_16k_cache_size
db_4k_cache_size
db_32k_cache_size
and so on?
If I have NO datafiles other than of the default block size, would I need to define a size for those other buffer pool? Is there any process that would benifit of these pools?
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Feb 28, 2013
I am executing a plsql procedure and trying to increase buffer size to display all characters, procedure is given below:
create or replace procedure prc_p(prm_t1 in VARCHAR2,
prm_t2 in VARCHAR2,
prm_tab in varchar2
)
AUTHID CURRENT_USER
as
str_sql VARCHAR2 (4000);
[code]..........
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Oct 9, 2009
I am binding parameters using obndra to Package. while executing with oexec it is giving error "ORA-01044: size 25600000 of buffer bound to variable exceeds maximum"
I am getting this error in Shared server only.In dedicated server it is working.
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Jun 20, 2013
What is the difference between cache fusion and Cache Coherency. Both are same or different functionality.
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Jul 22, 2013
I am trying to practice some RMAN configuration settings.Version 11.2.0.1OS - Linux X86-64 What i wanted to validate is if there is no level 0 backup of database taken, then the level 1 backup will be automatically backing up all the blocks of the database(similar to full backup). RMAN> report schema; Report of database schema for database with db_unique_name DB101 List of Permanent Datafiles
File Size(MB) Tablespace RB segs Datafile Name----1 300 SYSTEM +DATA/db101/datafile/system.257.8208254172 200 SYSAUX *** +DATA/ db101/ datafile/sysaux.268.8208254253 820 UNDOTBS1 *** +DATA/db101/datafile/undotbs1.261.8208254294 5000 TPCCTAB *** +DATA/ db101/ datafile/tpcctab.266.820832485 List of Temporary Files=File Size(MB) Tablespace Maxsize(MB) Tempfile Name---- 1 200..
[code]....
I am not sure what these input bytes are which is not matching with the database size(posted in the beginning of thread)? why it has to show as db full when i actually run a incremental?
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Jul 10, 2012
I have some question.
TTversion : TimesTen Release 11.2.2.3.0 (64 bit Linux/x86_64) (tt112230:53376) 2012-05-24T09:20:08Z
We are testing a AWT cache group ( with CacheAwtParallelism=4 ).
Application(1 process) to the DML generates to TimesTen(DSN=TEST).
At this point, Are delivered to the 4 parallel DML?
[TEST]
Driver=/home/TimesTen/tt112230/lib/libtten.so
DataStore=/home/TimesTen/DataStore/TEST/test
PermSize=1024
TempSize=512
PLSQL=1
[code].......
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Mar 2, 2010
I have to create a spool file using pl/sql (Oracle 10g/Solaris environment) and then copy the file from solaris environment to sharepoint(windows machine) folder. How to implement this(copy to sharepoint ) in pl/sql.
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May 28, 2013
I am having 11gr2 database on a 2 node RAC cluster . OS is RHEL version 5.8When i change the SGA_MAX_SIZE to 5GB, after i bounce it shows as 15GB.
I am trying to set my SGA_TARGET and SGA_MAX_SIZE to 5G. But after bouncing SGA_MAX_SIZE is showing as 15GB and not as 5GB
I also tried edit in pfile and then create spfile and started up with spfile. But still same i am observing.
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Dec 26, 2011
I write a Function in PL/SQL to consume a webservice and its working fine when i run in TOAD or SQL terminal. But when i try it from oracle form developer 6i , it gives me the following error :
ORA-00600: internal error code, arguments: [26599], [1], [211], [], [], [], [], []
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Aug 31, 2010
When I was going through the Enterprise Manager Grid Control, I found an error due to which I looked at the trace file and it said:
ORA-07445: exception encountered: core dump ACCESS_VIOLATION unable_to_trans_pc PC:0x7C81BD02 ADDR:0x49444E49 UNABLE_TO_READ]
I searched and found that it has something to do with the SGA parameters. I saw that the shared_pool_size and the sga_target paramters are set to 0...Also there are certain SQLs hanging at some point. I thought I should change the above mentioned parameters.
My question now is, can I use the Alter System statements from the SQL Plus to change these parameters, and do they change immediately or do I need to reboot the Oracle instance for those changes to take effect? I would like to do:
alter system set sga_target=400m;
alter system set shared_pool_size=200m;
would these work and take effect immediately?
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Jun 15, 2012
What value should i set for sga_target in my oracle 10g database?
Currently -
sga_max_size = 32GB
pga_aggregate_target = 6GB
RAM on server = 64 GB
I'll need to disable db_block_buffers parameters in order to enable sga_target. right?
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May 8, 2013
We are planning to export the table data to a file pipedelimited. How do i estimate the size of the FlatFile based on the table size? or avg rowlength
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