Performance Tuning :: Demonstrate Working Of OCI Client Result Cache?
Jan 2, 2013
I'm trying to demonstrate the working of the OCI client result cache. I've set some parameters,orcl> sho parameter result_cache
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
client_result_cache_lag big integer 3000
client_result_cache_size big integer 1000000
result_cache_max_result integer 5
result_cache_max_size big integer 1984K
result_cache_mode string FORCE
result_cache_remote_expiration integer 0
If I understand the docs correctly, that should be all that is needed.I've complied and run the cdemoqc and cdemoqc2 OCI demos, but I never get anything in the V$CLIENT_RESULT_CACHE_STATS or CLIENT_RESULT_CACHE_STATS$ views. This is probably because the sessions exit after running the queries.
So I've also tried repeating arbitrary queries through cdemo2, which gives a persistent session, but there is still nothing in those views and furthermore the v$result_cache_objects.scan_count for my queries keeps increasing. So I don't think think the client side cache is working.
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
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.
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 ?
In order to improve the performance of our live server, I am trying to do an exhaustive comparison with our test environment which is quite quick in spite of the fact that we port the data from Live every month.
There are no obviously slow queries appearing in the the top SQLs of AWR, we have optimised such things already. Right now it is about general uplift rather than SQL based tuning.
I picked up random SQLs and I noticed a marked differences in the execution time. Typically they are 3 to 4 times and there are cases much more than that.
1. I observed that, while the explain plan of the queries are same, trace of the queries give a different picture. I have observed that the recursive calls, consistent gets and sorts(memory) are quite high on Live. 2. I have no solid reasons to say this but my instincts tell me that the recursive calls is the major contributing factor. It is sometimes 2000+ for an SQL. 3. On googling more on that, it finally made me compare the data dictionary on the AWR report of test and Live.
The dc_objects caught my eyes. In that 4 hour AWR, there were about 10 million get requests and the pct miss was ~10. For similar load, the test server had 5 million gets with 0.08 PCT miss for 4 hours.
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.
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.
i am testing a proc after tuning it but the problem is, it is taking a very very less time which it shouldn't. I know that it is because of the buffer cache and the shared pool. that why i need to clean the cache to retest it.
I cannot bounce the database as other schemas are part of it. so is there any way to clean the cache for that particular schema i.e bouncing any particular schema(i know that the term is not appropriate).
I have a query with FULL hint that is behaving in a strange manner. The query fetches around 700000 of data. Sometimes it fetches the data with the hint and sometimes it does not fetch any data with the hint and then I have to remove the hint and have to fetch the data. Below is the query,
Oracle UNION ALL performance issue: when I try to run below SQL query separately SQL part1 and SQL part2 it takes some seconds only but if I run together with group by and without group by it take much time.
SELECT AVG(date_completed-login_date),to_char(to_date(login_date), 'YYYY') as wYear FROM ( SELECT test.date_completed 'date_completed',sample.login_date 'login_date') FROM sample test where (some conditions) ) ---SQL part 1 UNION ALL
In Oracle 11g/R2, I created replica of HR.Employees table & executed the following statement (+Although using SUM() function is non-logical in this case, but just testifying the result+)
STEP - 1
SELECT /+ RESULT_CACHE */ employee_id, first_name, last_name, SUM(salary)* FROM HR.Employees_copy WHERE department_id = 20 GROUP BY employee_id, first_name, last_name;
EMPLOYEE_ID FIRST_NAME LAST_NAME SUM(SALARY) ------------------------------------------------------------------------------------------------------- 202 Pat Fay 6000 201 Michael Hartstein 13000
Elapsed: 00:00:00.01
Execution Plan ---------------------------------------------------------- Plan hash value: 3837552314 -------------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | -------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 2 | 130 | 4 (25)| 00:00:01 | | 1 | RESULT CACHE | 3acbj133x8qkq8f8m7zm0br3mu | | | | | | 2 | HASH GROUP BY | | 2 | 130 | 4 (25)| 00:00:01 | |* 3 | TABLE ACCESS FULL | EMPLOYEES_COPY | 2 | 130 | 3 (0)| 00:00:01 |
Statistics ---------------------------------------------------------- 0 recursive calls 0 db block gets 0 consistent gets 0 physical reads 0 redo size *690* bytes sent via SQL*Net to client 416 bytes received via SQL*Net from client 2 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 2 rows processed
STEP - 2
INSERT INTO HR.employees_copy VALUES(200, 'Dummy', 'User','Dummy.User@email.com',NULL, sysdate, 'MANAGER',5000, NULL,NULL,20);
STEP - 3
SELECT /*+ RESULT_CACHE */ employee_id, first_name, last_name, SUM(salary) FROM HR.Employees_copy WHERE department_id = 20 GROUP BY employee_id, first_name, last_name;
EMPLOYEE_ID FIRST_NAME LAST_NAME SUM(SALARY) -------------------------------------------------------------------------------------------------- 202 Pat Fay 6000 201 Michael Hartstein 13000 200 Dummy User 5000
Elapsed: 00:00:00.03
Execution Plan ---------------------------------------------------------- Plan hash value: 3837552314
Statistics ---------------------------------------------------------- 0 recursive calls 0 db block gets 4 consistent gets 0 physical reads 0 redo size *714* bytes sent via SQL*Net to client 416 bytes received via SQL*Net from client 2 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 3 rows processed
In the execution plan of STEP-3, against ID-1 the operation RESULT CACHE is shown which shows the result has been retrieved directly from Result cache. Does this mean that Oracle Server has Incrementally Retrieved the resultset?
Because, before the execution of STEP-2, the cache contained only 2 records. Then 1 record was inserted but after STEP-3, a total of 3 records was returned from cache. Does this mean that newly inserted row is retrieved from database and merged to the cached result of STEP-1?
If Oracle server has incrementally retrieved and merged newly inserted record, what mechanism is being used by the Oracle to do so?
I have an application built in Apex 4.2It's been running fine for several weeksI've not made any changes to the codeSuddenly it developed what seems to be a cache problem.If I enter a search criteria; it displays results. I enter a different search criteria and it brings back the same results as the first criteria.I enter a search criteria in a different field and I still get the results from the first searchI go from Internet Explorer to Mozilla.
DIfferent search criteria, but same issue. Google chrome - same issueThe obvious answer is to clear the cache.I have a process set up that is clear Cache for Items , on submit after computations and validations and then I list all the items individually.This process has been there all along.
I never had this problem before.If I log out and come back in, same issue. What ever I enter as the first search criteria is the results no matter how I search
I have an Oracle database (9.2.0.7) installed on a HP-UX server.When trying to access this database from another HP-UX or Linux server, connection is fine. But when trying to connect from a Windows based client, connection is very slow (almost 1 minute to return the result of a 'select count(*)' like query, which is immediate from the Linux client).
Here are some facts I can add :
- Clients and servers are on the same network segment (it is not a network matter)
- No matter which client version I use, there no difference
- I tried to know what happens on the Oracle server when performing my sample query using tusc command : the result is that the server is performing exactly the same actions when sending my query from a Linux client or a Windows client
- The only relevant difference seems to be the client OS
I need to install Oracle client to get latest sql plus working on client pc as the problem is, i am not able to find out where i can download this , i just need the sql plus as i am not able use many commands because when i installed oracle forms 6i client tool , sql plus 8.0 got installed.
Looking to understand the difference between instance tuning and database tuning.
What is the difference between these two tuning exercises? I understand that an instance is memory based structures (logical) where as database consists of physical structures.
However, how does one tune a database the physical structure? Does it have to do with file placements/block sizes etc. Would you agree that a lot of that is taken care by ASM now in 11g? What tools are required/available (third party as well as oracle supplied) for these types of tuning scenarios?
I have two tables with 113M records in DWH_BILL_DET & 103M in prd_rerate_chg_que and Im running following merge query, which is running for 13 hrs to update records, which is quiet longer time.
SQL> explain plan for MERGE /*+ parallel (rq, 16) */ INTO DWH_BILL_DET rq USING (SELECT rated_que_rowid, detail_rerate_flag_code, rerate_sel_key,
How the length of column width effects index performance?
For example if i had IOT table emp_iot with columns: (id number, job varchar2(20), time date, plan number)
Table key consist of(id, job, time)
Column JOB has fixed list of distinct values ('ANALYST', 'NIGHT_WORKED', etc...).
What performance increase i could expect if in column "job" i would store not names but concrete numbers identifying job names. For e.g. i would store "1" instead 'ANALYST' and "2" instead 'NIGHT_WORKED'.
I have a question about database fragmentation.I know that fragmentation can reduce performance in query times. The blocks are distributed in many extents and scans process takes a long time. Oracle engine have to locate the address of the next extent..
I want to know if there is any system view in which you can check if your table or index has high fragmentation. If it's needed I will have to re-create, move or rebulid the table or index, but before I want to know if the degree of fragmentation is high.
Any useful script or query to do this, any interesting oracle system view?
There is a simple way to increase the performance of a query by reducing the row-size of the table it hits. I used it in the past by dividing the table into smaller parts and querying respective smaller table in each query.
what is this method called ? just forgot the method and can't recall it. what this type of row-reduction optimization is called ?
How many records could I have in a single table without performance degradation with Standard Edition without partitioning with cutting-edge server (8 or 12 cores, 72 GB RAM, FC 4 Gbit, etc...) and good storage?
300 Millions in only one table with 500K transactions / day is too much?
Testing our 9i to 11g upgrade, we've imported the entire DB into the new machine.We've found that certain procedures are really suffering performance problems. BUT, we've also found, that if we check out a production copy of the procedure from our source code control, and reinstall it, the performance issue goes away. Just alter the procedure and recompiling does NOT work.
The new machine where the 11g database exists is slightly different than the source, but it's not like we have this problem with every procedure. It's only a couple.
any possible reason that we'd have to re-install a procedure to correct a performance problem?
I need to check the package performance and need to improve the package performance.
1. how to check the package performance(each and every statement in the package)? 2. In the package using the delete statement to delete all records and observed that delete is taking long time to delete all the records in the table(Table records 7000000). This table is like staging table.Daily need to clean the data before inserting the data into it. what can I use instead of Delete.
Somewhere I read that we should not use hints in Oracle production environments, but we can use hints in the development environment and on achieving the desired execution plan we can adjust the 'statistics' to follow that plan without hints.
Q1. If it is true what statistics do we adjust for influencing the execution plan and how?
For example, I have the following simple query:
select e.empid, e.ename, d.dname from emp e, dept d where e.deptno=d.deptno;
emp.empid, emp.deptno and dep.deptno columns have indexes and the tables have the standard structure as found in the basic oracle examples.
If I look at the execution plan of the above query then I see that the driving table is empand the driven table is dept.Also the type of join that is taking place is 'Nested Loop'.
Questions: With respect to the above query, Q 2. If I want to make dept the driving table and emp the driven table then how can I adjust the statistics to achieve that? Q 3. If I want to use hash join instead of a nested loop join then then how can I adjust the statistics to achieve that?
I can put the ordered and the use_hash hint to effect this but again I have heard that altering statistics is a more robust way to control an execution plan as compared to hints.
