Data Buffer Cache Limit
Is there any way that I could signal daat buffer cache to write all data to data files if amount of dirty blocks reach say 50 Mb.
Iam processing with BLOBS, one blob at a time, some of which has sizes exceeeding 100 Mb and the diffcult thing is that I cannot write to disk until the whoile blob is finished as it is one transaction.
Well if anyone is going to suggest that to open, process close, commit ....well i tried that but it also gives error "nmo free buffer pool" but this comes for twice the size of buffer size = 100 Mb file when db cache size is 50 mb.
any ideas.
Hello,
Ia using Oracle 9.0.1.3.1
I am getting error ORA-OO379 No free Buffers available in Buffer Pool. Default for block size 8k.
My Init.ora file is
# Copyright (c) 1991, 2001 by Oracle Corporation
# Cache and I/O
db_block_size=8192
db_cache_size=104857600
# Cursors and Library Cache
open_cursors=300
# Diagnostics and Statistics
background_dump_dest=C:\oracle\admin\iasdb\bdump
core_dump_dest=C:\oracle\admin\iasdb\cdump
timed_statistics=TRUE
user_dump_dest=C:\oracle\admin\iasdb\udump
# Distributed, Replication and Snapshot
db_domain="removed"
remote_login_passwordfile=EXCLUSIVE
# File Configuration
control_files=("C:\oracle\oradata\iasdb\CONTROL01.CTL", "C:\oracle\oradata\iasdb\CONTROL02.CTL", "C:\oracle\oradata\iasdb\CONTROL03.CTL")
# Job Queues
job_queue_processes=4
# MTS
dispatchers="(PROTOCOL=TCP)(PRE=oracle.aurora.server.GiopServer)", "(PROTOCOL=TCP)(PRE=oracle.aurora.server.SGiopServer)"
# Miscellaneous
aq_tm_processes=1
compatible=9.0.0
db_name=iasdb
# Network Registration
instance_name=iasdb
# Pools
java_pool_size=41943040
shared_pool_size=33554432
# Processes and Sessions
processes=150
# Redo Log and Recovery
fast_start_mttr_target=300
# Sort, Hash Joins, Bitmap Indexes
pga_aggregate_target=33554432
sort_area_size=524288
# System Managed Undo and Rollback Segments
undo_management=AUTO
undo_tablespace=UNDOTBS
Similar Messages
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Data Buffer Cache Error Message
I'm using a load rule that builds a dimenson on the fly and getting the following error: "Not enough memory to allocate the Data Buffer Cache [adDatInitCacheParamsAborted]"I've got 4 other databases which are set up the same as this one and I'm not getting this error. I've checked all the settings and I think they're all the same.Anyone have any idea what this error could mean?I can be reached at [email protected]
Hi,
Same issue, running Vista too. This problem is recent. It may be due to the last itunes update. itunes 11.2.23 -
Data buffer cache has undo information...??
do data buffer in sga has any undo information....??
920273 wrote:
in sga we have data buffer ..... in data buffer cache if i m updating a block, do any undo information is maintained in buffer cache regarding the change, i hav made in block.....am
lets take an example if i m updating a block having value '2' to '4'...and dbwriter not writes to datafiles ...in this case do any undo information is maintained in buffer cache...???Hmmm.. When you updated value 2 to 4, so still its uncommitted then the transaction is active and it will be in buffer cache itself. Of course if the cache is full or performed any checkpoint, then this modified data also writtened into data files. So you should not mention dbwriter not writes to datafiles you cant predict when cache going to full or checkpoint occurred. -
Hi Guru(s),
Please anyone can tell me that, how can we check the size of data buffer cache.
Please help.
Regards,
Rajeev KHi,
Here is what I would do:
First, let's have a look what views we have available to us
SQL> select table_name from dict where table_name like '%SGA%';
TABLE_NAME
DBA_HIST_SGA
DBA_HIST_SGASTAT
DBA_HIST_SGA_TARGET_ADVICE
V$SGA
V$SGAINFO
V$SGASTAT
V$SGA_CURRENT_RESIZE_OPS
V$SGA_DYNAMIC_COMPONENTS
V$SGA_DYNAMIC_FREE_MEMORY
V$SGA_RESIZE_OPS
V$SGA_TARGET_ADVICE
GV$SGA
GV$SGAINFO
GV$SGASTAT
GV$SGA_CURRENT_RESIZE_OPS
GV$SGA_DYNAMIC_COMPONENTS
GV$SGA_DYNAMIC_FREE_MEMORY
GV$SGA_RESIZE_OPS
GV$SGA_TARGET_ADVICE
19 rows selected.v$sgainfo looks pretty promising, what does it contain?
SQL> desc v$sgainfo
Name Null? Type
NAME VARCHAR2(32)
BYTES NUMBER
RESIZEABLE VARCHAR2(3)And how many rows are in it?
SQL> select count(*) from v$sgainfo;
COUNT(*)
12Not too many so let's look at them all, with a little formatting
SQL> select name,round(bytes/1024/1024,0) MB, resizeable from v$sgainfo order by name;Hope that helps,
Rob -
Hi All,
Can somebody please please tell some ways in which i can improve the data buffer quality? Presently it is 51.2%. The DB is 10.2.0.2.0
I want to know, wat all factors do i need to keep in mind if i want to increase DB_CACHE_SIZE?
Also, i want to know how can i find out Cache Hit ratio?
Further, i want to know which are the most frequently accessed objects in my DB?
Thanks and Regards,
Nick.Nick-- wud b DBA wrote:
Hi Aman,
Thanks. Can u please give the appropriate query for that?
And moreover when i'm giving:
SQL>desc V$SEGMENT-STATISTICS; It is giving the following error:
SP2-0565: Illegal identifier.
Regards,
Nick.LOL dude I put it by mistake. Its dash(-) sign but we need underscore(_) sign.
About the query, it may vary what you really mean by "most used obect". If you mean to find the object that is undergoing lots of reads,writes than this may help,
SELECT Rownum AS Rank,
Seg_Lio.*
FROM (SELECT St.Owner,
St.Obj#,
St.Object_Type,
St.Object_Name,
St.VALUE,
'LIO' AS Unit
FROM V$segment_Statistics St
WHERE St.Statistic_Name = 'logical reads'
ORDER BY St.VALUE DESC) Seg_Lio
WHERE Rownum <= 10
UNION ALL
SELECT Rownum AS Rank,
Seq_Pio_r.*
FROM (SELECT St.Owner,
St.Obj#,
St.Object_Type,
St.Object_Name,
St.VALUE,
'PIO Reads' AS Unit
FROM V$segment_Statistics St
WHERE St.Statistic_Name = 'physical reads'
ORDER BY St.VALUE DESC) Seq_Pio_r
WHERE Rownum <= 10
UNION ALL
SELECT Rownum AS Rank,
Seq_Pio_w.*
FROM (SELECT St.Owner,
St.Obj#,
St.Object_Type,
St.Object_Name,
St.VALUE,
'PIO Writes' AS Unit
FROM V$segment_Statistics St
WHERE St.Statistic_Name = 'physical writes'
ORDER BY St.VALUE DESC) Seq_Pio_w
WHERE Rownum <= 10; But if you are looking for the objects which are most highly in the waits than this query may help
select * from
select
DECODE
(GROUPING(a.object_name), 1, 'All Objects', a.object_name)
AS "Object",
sum(case when
a.statistic_name = 'ITL waits'
then
a.value else null end) "ITL Waits",
sum(case when
a.statistic_name = 'buffer busy waits'
then
a.value else null end) "Buffer Busy Waits",
sum(case when
a.statistic_name = 'row lock waits'
then
a.value else null end) "Row Lock Waits",
sum(case when
a.statistic_name = 'physical reads'
then
a.value else null end) "Physical Reads",
sum(case when
a.statistic_name = 'logical reads'
then
a.value else null end) "Logical Reads"
from
v$segment_statistics a
where
a.owner like upper('&owner')
group by
rollup(a.object_name)) b
where (b."ITL Waits">0 or b."Buffer Busy Waits">0)This query's reference:http://www.dba-oracle.com/t_object_wait_v_segment_statistics.htm
So it would depend upon that on what ground you want to get the objects.
About the cache increase, are you seeing any wait events related to buffer cache or DBWR in the statspack report?
HTH
Aman.... -
How data buffer cache is handled
hi all,
I have a doubt in how buffer cache is managed.. I read that server process will read blocks from data file and keeps them in buffer cache if they are not already present in buffer cache.. Suppose two users from different sessions issue the same statement at the same time, and they are picked up by different server processes, and upon checking they will find that the block is not present in SGA, so they both will go read the block.. is it not unnecessary.. or am i wrong? please let me know how it is handled.
Regards
SureshHi tinku,
I understand what you mean.. but my problem is different.
suppose there are two sessions
first session issues a statement:
Select * from emp where empno = 12;
and second session issues
select * from emp where empno in (12,13);
becoz these two statements are different, these two statements are to be parsed separately. After parsing, each of the server processes will see if the block corresponding 12 is already in memory, if it is not, they will read it from data file and keep in buffer cache.. suppose these two server processes at the same time find that the block is not in SGA and try to read the block from data file, there would be two copies of the block in SGA. isn't it. I don't think this is what is gonna happen. so i need how the server processes coordinate with each other to read only necessary blocks without redundancy.
Regards
Suresh -
Hi Guru,
Can anyone tell me what is the actual definition of Data buffer Cache & Log buffer Cache and how it works in Oracle 10g??
Please
Regards,
Rajeev,India
Edited by: 970371 on Nov 8, 2012 7:06 PMvlethakula wrote:
Databuffer cache contains the blocks which are read from physical data files.Database buffer cache contains buffers that hold the blocks read from the disk.
Log buffer cahce contains changes made to the database
e.g: You try to update a row, the changes made to that row is written in form of change vectors to Log buffer cache, from there on certail rules(like commit) LGWR background process writes those changes from LOG BUFFER CACHE to redo log files.
The block which is modified in database buffer cache, will be written to physical files by DBWR process after certain rules are met (like checkpoint)The reason that I didn't give the explanation or the links containing the same from the docs that I wanted OP to come up with some sort of his own understanding about the two caches first.
Aman.... -
can anyone plz clarify my doubt,it is which parameter defines the size of db buffer cache in the SGA.does db_cache_size directly defines the size or is it the size of the cache of standard blocks(specified by db_block_size parameter).
DB_BLOCK_BUFFERS specifies the number of blocks to allocate for data buffer. This parameter's value is then multiplied with DB_BLOCK_SIZE to calculate the size of the data buffer.
DB_CACHE_SIZE specifies the size value itself directly in units of KV,MB or GB. This parameter alone is enough to calculate the data buffer cache size.
DB_BLOCK_BUFFERS can only create buffer cache in units of blocks based on one parameter DB_BLOCK_SIZE. On the other hand, multiple data buffere caches can be created by using DB_nK_CACHE_SIZE parameters where n is the blocks's size of for the buffer cache. So for example, one can allocate X MB buffer cache of 8K block size and have Y MB buffer cache of 16K blocks. This helps when you have tablespaces of varying block sizes (This could not be possible using DB_BLOCK_BUFFERS as DB_BLOCK_SIZE is not modifiable).
DB_CACHE_SIZE can work along with SGA_TARGET parameter (which decides SGA size). If DB_CACHE_SIZE is 0, then it's value varies based on usage. If a value is set then that value turns out to be a minimum value. This is not possible using DB_BLOCK_BUFFERS. -
Buffer cache vs data blocks that can be cache
Hi Guys,
Do it means that if we have 2 GB of buffer cache allocated to Oracle, we can only store up to 2GB of data in memory?
thanksdbaing wrote:
Hi Guys,
Do it means that if we have 2 GB of buffer cache allocated to Oracle, we can only store up to 2GB of data in memory?Yes, this means that you can any time, can have 2gb of cached blocks in your memory.
Aman.... -
Data being fetched bigger than DB Buffer Cache
DB Version: 10.2.0.4
OS : Solarit 5.10
We have a DB with 1gb set for DB_CACHE_SIZE . Automatic Shared Memory Management is Disabled (SGA_TARGET = 0).
If a query is fired against a table which is going retrieve 2GB of data. Will that session hang? How will oracle handle this?Tom wrote:
If the retrieved blocks get automatically removed from the buffer cache after it is fetched as per LRU algorithm, then Oracle should handle this without any issues. Right?Yes. No issues in that the "+size of a fetch+" (e.g. selecting 2GB worth of rows) need to fit completely in the db buffer cache (only 1GB in size).
As Sybrand mentioned - everything in that case will be flushed as newer data blocks will be read... and that will be flushed again shortly afterward as even newer data blocks are read.
The cache hit ratio will thus be low.
But this will not cause Oracle errors or problems - simply that performance degrade as the data volumes being processed exceeds the capacity of the cache.
It is like running a very large program that requires more RAM than what is available on a PC. The "extra RAM" comes from the swap file on disk. App program will be slow as its memory pages (some on disk) needs to be swapped into and out of memory as needed. It will work faster if the PC has sufficient RAM. However, the o/s is designed to deal with this exact situation where more RAM is needed than what physically available.
Similar situation with processing larger data chunks than what the buffer cache has capacity for. -
Hello -
We have 3 x EX2010 SP3 RU5 nodes in a cross-site DAG.
Multi-role servers with 18 GB RAM [increased from 16 GB in an attempt to clear this warning without success].
We run nightly backups on both nodes at the Primary Site.
Node 1 backup covers all mailbox databases [active & passive].
Node 2 backup covers the Public Folders database.
The backups for each database are timed so they do not overlap.
During each backup we get several of these event log warnings:
Log Name: Application
Source: ESE
Date: 23/04/2014 00:47:22
Event ID: 906
Task Category: Performance
Level: Warning
Keywords: Classic
User: N/A
Computer: EX1.xxx.com
Description:
Information Store (5012) A significant portion of the database buffer cache has been written out to the system paging file. This may result in severe performance degradation.
See help link for complete details of possible causes.
Resident cache has fallen by 42523 buffers (or 27%) in the last 903 seconds.
Current Total Percent Resident: 26% (110122 of 421303 buffers)
We've rescheduled the backups and the warning message occurences just move with the backup schedules.
We're not aware of perceived end-user performance degradation, overnight backups in this time zone coincide with the business day for mailbox users in SEA.
I raised a call with the Microsoft Enterprise Support folks, they had a look at BPA output and from their diagnostics tool. We have enough RAM and no major issues detected.
They suggested McAfee AV could be the root of our problems, but we have v8.8 with EX2010 exceptions configured.
Backup software is Asigra V12.2 with latest hotfixes.
We're trying to clear up these warnings as they're throwing SCOM alerts and making a mess of availability reporting.
Any suggestions please?
Thanks in advanceHaving said all that, a colleague has suggested we just limit the amount of RAM available for the EX2010 DB cache
Then it won't have to start releasing RAM when the backup runs, and won't throw SCOM alerts
This attribute should do it...
msExchESEParamCacheSizeMax
http://technet.microsoft.com/en-us/library/ee832793.aspx
Give me a shout if this is a bad idea
Thanks -
10G NEW FEATURE-HOW TO FLUSH THE BUFFER CACHE
제품 : ORACLE SERVER
작성날짜 : 2004-05-25
10G NEW FEATURE-HOW TO FLUSH THE BUFFER CACHE
===============================================
PURPOSE
이 자료는 Oracle 10g new feature 로 manual 하게
buffer cache 를 flush 할 수 있는 기능에 대하여 알아보도록 한다.
Explanation
Oracle 10g 에서 new feature 로 소개된 내용으로 SGA 내 buffer cache 의
모든 data 를 command 수행으로 clear 할 수 있다.
이 작업을 위해서는 "alter system" privileges 가 있어야 한다.
Buffer cache flush 를 위한 command 는 다음과 같다.
주의) 이 작업은 database performance 에 영향을 줄 수 있으므로 주의하여 사용하여야 한다.
SQL > alter system flush buffer_cache;
Example
x$bh 를 query 하여 buffer cache 내 존재하는 정보를 확인한다.
x$bh view 는 buffer cache headers 정보를 확인할 수 있는 view 이다.
우선 test 로 table 을 생성하고 insert 를 수행하고
x$bh 에서 barfil column(Relative file number of block) 과 file# 를 조회한다.
1) Test table 생성
SQL> Create table Test_buffer (a number)
2 tablespace USERS;
Table created.
2) Test table 에 insert
SQL> begin
2 for i in 1..1000
3 loop
4 insert into test_buffer values (i);
5 end loop;
6 commit;
7 end;
8 /
PL/SQL procedure successfully completed.
3) Object_id 확인
SQL> select OBJECT_id from dba_objects
2 where object_name='TEST_BUFFER';
OBJECT_ID
42817
4) x$bh 에서 buffer cache 내에 올라와 있는 DBARFIL(file number of block) 를 조회한다.
SQL> select ts#,file#,dbarfil,dbablk,class,state,mode_held,obj
2 from x$bh where obj= 42817;
TS# FILE# DBARFIL DBABLK CLASS STATE MODE_HELD J
9 23 23 1297 8 1 0 7
9 23 23 1298 9 1 0 7
9 23 23 1299 4 1 0 7
9 23 23 1300 1 1 0 7
9 23 23 1301 1 1 0 7
9 23 23 1302 1 1 0 7
9 23 23 1303 1 1 0 7
9 23 23 1304 1 1 0 7
8 rows selected.
5) 다음과 같이 buffer cache 를 flush 하고 위 query 를 재수행한다.
SQL > alter system flush buffer_cache ;
SQL> select ts#,file#,dbarfil,dbablk,class,state,mode_held,obj
2 from x$bh where obj= 42817;
6) x$bh 에서 state column 이 0 인지 확인한다.
0 은 free buffer 를 의미한다. flush 이후에 state 가 0 인지 확인함으로써
flushing 이 command 를 통해 manual 하게 수행되었음을 확인할 수 있다.
Reference Documents
<NOTE. 251326.1>I am also having the same issue. Can this be addressed or does BEA provide 'almost'
working code for the bargin price of $80k/cpu?
"Prashanth " <[email protected]> wrote:
>
Hi ALL,
I am using wl:cache tag for caching purpose. My reqmnt is such that I
have to
flush the cache based on user activity.
I have tried all the combinations, but could not achieve the desired
result.
Can somebody guide me on how can we flush the cache??
TIA, Prashanth Bhat. -
What else are stored in the database buffer cache?
What else are stored in the database buffer cache except the data blocks read from datafiles?
That is a good idea.
SQL> desc v$BH;
Name Null? Type
FILE# NUMBER
BLOCK# NUMBER
CLASS# NUMBER
STATUS VARCHAR2(10)
XNC NUMBER
FORCED_READS NUMBER
FORCED_WRITES NUMBER
LOCK_ELEMENT_ADDR RAW(4)
LOCK_ELEMENT_NAME NUMBER
LOCK_ELEMENT_CLASS NUMBER
DIRTY VARCHAR2(1)
TEMP VARCHAR2(1)
PING VARCHAR2(1)
STALE VARCHAR2(1)
DIRECT VARCHAR2(1)
NEW CHAR(1)
OBJD NUMBER
TS# NUMBERTEMP VARCHAR2(1) Y - temporary block
PING VARCHAR2(1) Y - block pinged
STALE VARCHAR2(1) Y - block is stale
DIRECT VARCHAR2(1) Y - direct block
My question is what are temporary block and direct block?
Is it true that some blocks in temp tablespace are stored in the data buffer? -
Will I increase my Buffer Cache ?
Oracle 9i
Shared Pool 2112 Mb
Buffer Cache 1728 Mb
Large Pool 32Mb
Java Pool 32 Mb
Total 3907.358 Mb
SGA Max Size 17011.494 Mb
PGA
Aggregate PGA Target 2450 Mb
Current PGA Allocated 3286059 KB
Maximum PGA Allocated (since Startup) 3462747 KB
Cache Hit Percentage 98.71%
The Buffer Cache Size advise is telling me that if I increase the Buffer Cache to 1930Mb i will get a 8.83 decrease in phyiscal reads (And its get better the more I increase it)
The question is .. can I safely increase it (In light of my current memory allocations) ? Is it worth it .. ?Two things stand out:
Your sga max size is 17Gb, but you are only using about 4Gb of it - so you seem to have 13Gb that you are not making best use of.
Your pga aggregate target is 2.4Gb, but you've already hit a peak of 3.4Gb - which means your target may be too small - so it's lucky you had all that spare memory which hadn't gone into the SGA. Despite the availability of memory, some of your queries may have been rationed at run-time to try to minimise the excess demand.
Is this OLTP or DSS - where do you really need the memory ? (Have a look in v$process to see the pga usage on a process by process level).
How many processes are allowed to connect to the database ? (You ought to allow about 2Mb - 4Mb per process to the pga_aggregate_target for OLTP) and at least 1Mb per process for the buffer cache.
Where do you see time lost ? time on disk I/O, or time on CPU ? What type of disk I/O, what's the nature of the CPU usage. These figures alone do not tell us what you should do with the spare memory you seem to have.
A simple response to your original question would be that you probably need to increase the pga_aggregate_target, and you might as well increase the buffer size since you seem to have the memory for both.
On the downside, changing the pga_aggregate_target could cause some execution plans to change; and changing the buffer size does change the limit size on a 'short' table, which can cause an increase in I/O as an unlucky side effect if you're a little heavy on "long" tablescans.
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
http://www.jlcomp.demon.co.uk -
DB buffer cache vs. SQL query & PL/SQL function result cache
Hi all,
Started preparing for OCA cert. just myself using McGraw Hill's exam guide. Have a question about memory structures.
Actually, DB buffer cache is used to copy e.g. SELECT queries result data blocks, that can be reused by another session (server process).
There is also additional otion - SQL query & PL/SQL function result cache (from 11g), where also stored the results of such queries.
Do they do the same thing or nevertheless there is some difference, different purpose?
thanks in advance...There is also additional otion - SQL query & PL/SQL function result cache (from 11g), where also stored the results of such queries.Result cache located in shared pool.So it is one component of shared pool.When server process execute query(and if you configured result cache) then result will store in shared pool.Then next execution time run time mechanism will detect and consider using result cache without executing this query(if data was not changed this is happen detection time)
Do they do the same thing or nevertheless there is some difference, different purpose?.Buffer cache and result cache are different things and purpose also,but result cache introduced to improve response time of query in 11g(but such mechanism also implemented in 10g subquery execution,in complex query).In buffer cache holds data blocks but not such results.
Edited by: Chinar on Nov 4, 2011 4:40 AM
(Removing lots of "But" word from sentences :-) )
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