ResultCache 11g in DNA

8/13/2019 ResultCache 11g in DNA

1/13

Why at all did we try Result Cache in DNA ?

11g Result Cache - An Introduction

DNA Set up - init.ora etc

Monitoring effectiveness in DNA

Pointers for further study

Q&A

11g Result Cache in DNA


2/13

Need for Result Cache in DNA

http://digitsr.data.yahoo.com:9999/?a=ren&p=lmr-summary

For a given property and date, it takes more than 90 seconds to loadall nine sections of this page.

Goal is to deploy a solution/work around such that multiple requestsof same property and date can be served with 10 seconds.

Bulk of the 90 seconds was spent on querying , disk I/O..

Typical Usage : Different analysts visit the page multiple times for aproperty / day

Solution / Work around : Enable oracle 11g result cache
http://digitsr.data.yahoo.com:9999/?a=ren&p=lmr-summaryhttp://digitsr.data.yahoo.com:9999/?a=ren&p=lmr-summaryhttp://digitsr.data.yahoo.com:9999/?a=ren&p=lmr-summaryhttp://digitsr.data.yahoo.com:9999/?a=ren&p=lmr-summary


3/13

Query result set is cachedCached Data is shared across executions and instances

Automatically marked stale if underlying data is changed

Uses a Slice of the Shared Pool

Flushing Shared Pool doesnot flush result cache.

Should test it thoroughly before using it in production.

MySQL has this feauture since a long time.

11gR1 issues

no longer an issue in R2Explicity call DBMS_RESULT_CACHE.FLUSH to free memory

only one latch was controlling result cache. ( problem )

11g Result Cache - An Introduction


4/13

Access Large Amount of Data & Return Few Rows

Execute Somewhat Frequently

Product Lookups / Customer Info

Based on Slowly Changing Data

Country / State / County / Zip Code

Remote Database DML does not Invalidate the local results cache

Be extra careful on stale results if remote dml.

Init.ora : Result_cache_remote_expiration

DNA doesnot remote dmls in DNA

11g Result Cache - Queries that Benefit


5/13

Choices to enable/use result cache feature :

init.ora : result_cache_mode= FORCE

Query Hint :

select /*+ result_cache*/ Deptno, sum(sal) from emp group by deptno

Table Annotation : alter table emp(mode force) ;

Session Mode : alter session set result_cache_mode= force ;

DNA ETL : uses query hint

DNA YREPORT uses Session Mode using a logon trigger

Turn on 11g Result Cache


6/13

Wont Work with : Temporary tables

SYS or SYSTEM tables

Sequences (NEXTVAL or CURRVAL)

Date/Time Functions SYSDATE, CURRENT_DATE,

SYS_TIMESTAMP, CURRENT_TIMESTAMP, etc

USERENV / SYS_CONTEXT (with non-constant variables)

SYS_GUID

YREPORT DNA : Date is passed as a string

11g Result Cache - Restrictions


7/13

Init.ora parameter changes in each reporting instance :

For Reporting Nodes :

Bumped Shared_pool from 4G to 6G

result_cache_max_size=512M result_cache_max_result=1

For ETL Nodes :

result_cache_max_result= 5 (default)

DNA Set up - init.ora etc
http://twiki.corp.yahoo.com/view/OperationsManagement/OracleRacBuildChecklist


8/13

Client_result_cache_size Client_result_cache_lag

Sqlnet.ora has few %_RESULT_CACHE_% parameters as well

Disabled in DNA. Did not do extensive tests on these.

Wip on figuring out which other application can potentially use this.

11g Result Cache - More Parameters


9/13

Result Cache Dictionary Views

V$RESULT_CACHE_STATISTICS :

V$RESULT_CACHE_MEMORY

V$RESULT_CACHE_OBJECTS

V$RESULT_CACHE_DEPENDENCY


10/13


Cron @ sp1-portaldb-001:/net/dba/scripts/automation/ResultCacheStickinessRpt.pl

Select Inst_id, UserName, Type, Namespace, Count(*) Cnt_SQL, SUM(Scan_Count) "Repeated Scans",Round(SUM(block_count) * 1024/1024/1024,2) "Memory Usage (MB)" , SUM(ROW_COUNT) "Rows" ,SUM(Invalidations) "Invalidations", Round(SUM(Scan_count)/Count(*),2) "Repeated Scans Over Cnt"

FROM gv$result_cache_objects a INNER JOIN dba_users b ON (a.creator_uid=b.user_id)WHERE Status = 'Published' AND type = 'Result'Group by Inst_id , UserName , type , Namespace Order by Inst_id;

InstID USERNAME TYPE NAMES CNT_SQL RepeatedScans

Memory Usage

(MB) Rows Inval idations

Repeated Scans

Over Cnt

2 DNA_RO Result PLSQL 8 14 0.01 8 0 1.75

2 MYETL Result PLSQL 158 9287400 0.15 158 0 58781.01

2 YREPORT Result SQL 5 9 0 5 0 1.8

3 YREPORT Result PLSQL 226 474 0.22 226 0 2.1

3 YREPORT Result SQL 656 699 0.94 7176 0 1.074 MYETL Result PLSQL 47 6472 0.05 47 0 137.7


11/13


Cron @ sp1-portaldb-001:/net/dba/scripts/automation/ResultCacheStickinessRpt.pl

Interval Total Sql Scan Hits

------------ ------------ ------------

0 to 5 2734 9525 to 10 46 282

10 to 15 9 103

15 to 20 9 149

20 to 25 2 46

25 to 30 5 129

30 to 35 5 16235 to 40 4 149

SELECT 5 * TRUNC (scan_count / 5) || ' to ' || 5 * (TRUNC (scan_count/ 5) + 1) "Interval",COUNT(1) "Total Sql", SUM(scan_count) "Scan Hits"FROM gv$result_cache_objects Where Status = 'Published'

AND type = 'Result' AND Namespace = 'SQL'GROUP BY TRUNC (scan_count / 5) ORDER BY 5 *TRUNC (scan_count / 5)


12/13

1) http://www.sfoug.org/Downloads/Oracle11g_Results_Cache_20100304.pdf

Pointers for further study
http://www.sfoug.org/Downloads/Oracle11g_Results_Cache_20100304.pdfhttp://www.sfoug.org/Downloads/Oracle11g_Results_Cache_20100304.pdf


13/13

THANK YOU

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ResultCache 11g in DNA