1. Database Tuning - Processes, Memory
ISYS366: Week 04
Database Tuning - Processes, Memory
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ISYS366 - Week 4

2. Reasons for tuning Online application needs to run faster
Batch application needs to run faster
Management wants the system to run faster
[get the idea???]
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3. Three aspects to performance tuning
Faster hardware
Effective database configuration
e.g., don’t size any part of the System Global Area (SGA) outside of memory
Effective application design
e.g., effective query construction, effective use of parallelism; denormalization
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4. Tuning the System Global Area
DB_CACHE_SIZE
DB_CACHE_SIZE
Tuning the System Global Area
Automatic shared memory management simplifies the configuration of the SGA by automatically distributing the memory in the SGA for the following memory pools:
Database buffer cache (default pool): DB_CASHE_SIZE
Shared pool: SHARED_POOL_SIZE
Large pool: LARGE_POOL_SIZE
Java pool: JAVA_POOL_SIZE
Streams pool: STREAMS_POOL_SIZE
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5. Understand your goals Improve performance of specific queries
Improve performance of applications
Improve overall performance
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6. Steps (in order) Tune the query Tune the application
Tune memory structures
Tune disk I/O
Detect and eliminate resource contention
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7. When to tune the application
Before application rollout
Relatively inexpensive
Prototype
Issues
Database size
Database structure
Centralized
Distributed
Activity levels
After application rollout
Relatively expensive
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8. Strategies Multiple CPUs Scheduling
Move specific applications to different servers
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9. Parallelism NOPARALLEL PARALLEL
specifies serial execution of an operation. This is the default.
PARALLEL
specifies parallel execution of an operation.
DEGREE
determines the degree of parallelism for an operation on a single instance. That is, the number of query servers used in the parallel operation.
Integer
use integer query servers.
DEFAULT
the default number of query servers used is calculated from the number of CPUs and the number of DEVICES storing tables to be scanned in parallel.
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10. Parallelism
PARALLEL
INSTANCES
determines the number of parallel server instances used in the parallel operation. This keyword is ignored if you do not have a parallel server.
integer
use integer instances
DEFAULT
use all available instances
Note: INSTANCES only applies to an instance using the Oracle Parallel Server
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11. Parallelism – Examples
The following command creates a table using 10 query servers, 5 to scan SCOTT.EMP and another 5 to populate EMP_DEPT:
CREATE TABLE emp_dept
PARALLEL (DEGREE 5)
AS SELECT * FROM scott.emp
WHERE deptno = 10;
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12. Parallelism – Examples
The following command creates an index using 10 query servers, 5 to scan SCOTT.EMP and another 5 to populate the EMP_IDX index:
CREATE INDEX emp_idx
ON scott.emp (ename)
PARALLEL 5;
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13. Parallelism – Examples
The following command changes the default number of query servers used to query the EMP table:
ALTER TABLE emp
PARALLEL (DEGREE 9);
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14. Parallelism – Examples
The following command causes the index to be rebuilt from the existing index by using 6 query servers, 3 each to scan the old and to build the new index:
ALTER INDEX emp_idx
REBUILD
PARALLEL 3;
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15. Parallelism – Examples
The following command performs tablespace recovery using 5 recovery processes on 5 instances in a parallel server, for a total of 25 (5 * 5) query servers:
ALTER DATABASE
RECOVER TABLESPACE binky
PARALLEL (DEGREE 5 INSTANCES 5);
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16. Tools – DBMS specific Statistics Scripts Server Manager
UTLBSTAT (Begin Statistics)
UTLESTAT (End Statistics – REPORT.TXT)
They must be modified
They could become very large, therefore they need to be put in a tablespace OTHER than SYSTEM
Remote databases
Server Manager
Data dictionary views (system level)
[ go over UTLBSTAT and UTLESTAT]
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17. The methods of Collecting statistics
1. DICTIONARY and DYNAMIC views
Oracle server displays all system statistics in the V$SYSSTAT view and uses many other views for performance and troubleshooting information. You can find culmative totals since the instance started and is often unhelpful. If the instance is often rarely shutdown the statistics may cover a long period and have little meaning.
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18. The methods of Collecting statistics
2. UTLBSTAT and UTLESTAT Utilities Using this utilities to gather performance figures over a well defined period say during the busiest time of day or end of the Month and produce a report.
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19. The methods of Collecting statistics
3. TOOLS Using oracle GUI tools -Diagonostics and Tuning Packs-which addresses many oracle Performance management areas such as Graphical monitoring analysis and automated tuning of oracle Database.
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20. The Steps before the UTLBSTAT and UTLESTAT
.To gather performance over a period of defined time. .Produce a Hard Copy report .Run the script from server manager connected as SYSDBA. .Set TIMED_STATISTICS to TRUE.
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21. UTLBSTAT and UTLESTAT
Utility to begin statistics and Utility to end statistics. These are basically predefined SQL scripts comes along with oracle .
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22. UTLBSTAT and UTLESTAT
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23. Report.txt Library cache statistics system statistics
Wait events statistics
Latch statistics
Rollback contention statistics
Buffer Busy Wait statistics
Dictionary cache statistics
I/O statistics per datafile/tablespace Period of measurement
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24. Tablespace for the scripts
The script connects as SYSDBA and creates tables in SYS's default TS SYSTEM. Before running the script create a New TS for this purpose and change SYS's default TS to this new one.
After finishing running the both the scripts change once again SYS's default TS to SYSTEM.
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25. UTLBSTAT
1)While first executing the UTLBSTAT script from the above path already mentioned )The script creates BEGIN and END tables and takes the snapshot of data from the dynamic performance tables(V$xxx) to collect initial statistics and stores these in the BEGIN tables.
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26. UTLESTAT
1)Execute the UTLESTAT as mentioned from the above path. 2)The script takes a new snapshot of data from the dynamic performance tables (V$xxx) to collect final statistics and stores these in the END tables. 3)The script creates DIFFERENCE tables where it stores the values of the substraction of the results of the initial statistics from the final statistics. 4)The script drops all the temporary views and tables. 5)The script generates a report by selecting the data from the DIFFERENCE tables.
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27. UTLBSTAT and UTLESTAT
Based on the Report.txt file information you can understand which areas the tuning is required .
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28. Application Tuning Denormalize tables Instead of:
create table employee (
fname char(15) not null, lname char(15) not null,
minit char(1), ssn char(9) not null,
bdate date, address char(30),
sex char(1), salary number(7),
superssn char(9), dno number(1),
start_date date default(sysdate) not null,
end_date date, primary key (ssn));
create table department
(dname varchar2(20),
dnumber number(1) primary key,
mgrssn char(9),
mgrstartdate date);
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29. Application Tuning Denormalize tables Use create table employee (
fname char(15) not null, lname char(15) not null,
minit char(1), ssn char(9) not null,
bdate date, address char(30),
sex char(1), salary number(7),
superssn char(9),
start_date date default(sysdate) not null,
end_date date,
dname varchar2(20),
dnumber number(1),
mgrssn char(9),
mgrstartdate date, primary key (ssn));
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30. Application Tuning Denormalize tables Instead of:
create table employee (
fname char(15) not null, lname char(15) not null,
minit char(1), ssn char(9) not null,
bdate date, address char(30),
sex char(1), salary number(7),
superssn char(9), dno number(1),
start_date date default(sysdate) not null,
end_date date, primary key (ssn));
create table dependent
(essn char(9) references employee(ssn),
dependent_name char(20),
sex char(1),
bdate date,
relationship char(15),
primary key (essn, dependent_name));
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31. Application Tuning Denormalize tables Use create table employee (
fname char(15) not null, lname char(15) not null,
minit char(1), ssn char(9) not null,
bdate date, address char(30),
sex char(1), salary number(7),
superssn char(9), dno number(1),
start_date date default(sysdate) not null,
end_date date, dependent_name char(20),
sex char(1), bdate date,
relationship char(15),
primary key (ssn, dependent_name));
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32. Application Tuning PARALLEL clause of ALTER/CREATE TABLE and INDEX
PARALLEL clause of SELECT
Oracle Optimizer
Use of INDEXes
EXPLAIN PLAN
SQL Trace
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33. Application Tuning Compiling PROCEDURES SQL statements must be
Parsed
Compiled
Stored in SGA
Procedures must be
Stored in memory
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34. Application Tuning A word about how operations access tables
SELECT without a WHERE causes a "full table scan" (TABLE ACCESS FULL)
Read multiple blocks into memory
Expensive with many rows and/or many users
Inexpensive with tables with few rows (faster than using an index)
/*+ FULL (employee) */
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35. Application Tuning PARALLEL clause of SELECT
SELECT /*+ PARALLEL(employee, 4) */
PARALLEL clause of SELECT with Parallel Server Option
SELECT /*+ PARALLEL(employee, 4, 2) */
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36. Application Tuning Oracle Optimizer OPTIMIZER_MODE in INIT.ORA RULE
COST
ANALYZE
Rows in a table
Distinct keys in an index
DBMS_UTILITY.ANALYZE_SCHEMA
analyses all tables in a schema
CHAINED_ROWS
rows that do not fit into an Oracle data block become “chained”
CHOOSE
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37. Application Tuning Use of INDEXes Indexes won't be used *IF*
String constant starts with a wildcard
Using a function in the where clause
IS [NOT] NULL !=
NOT IN
Leading value of a multicolumn index is not set to equal a value
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38. Application Tuning EXPLAIN PLAN explain plan
set statement_id = 'MYTEST'
for
select ssn, dnumber from employee, department
where dno = dnumber;
SQL> select * From plan_table where statement_id = 'MYTEST';
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39. Application Tuning EXPLAIN PLAN SQL> desc plan_table
Name Null? Type
STATEMENT_ID VARCHAR2(30)
TIMESTAMP DATE
REMARKS VARCHAR2(80)
OPERATION VARCHAR2(30)
OPTIONS VARCHAR2(30)
OBJECT_NODE VARCHAR2(128)
OBJECT_OWNER VARCHAR2(30)
OBJECT_NAME VARCHAR2(30)
OBJECT_INSTANCE NUMBER(38)
OBJECT_TYPE VARCHAR2(30)
OPTIMIZER VARCHAR2(255)
SEARCH_COLUMNS NUMBER
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40. Application Tuning EXPLAIN PLAN Continued … ID NUMBER(38)
PARENT_ID NUMBER(38)
POSITION NUMBER(38)
COST NUMBER(38)
CARDINALITY NUMBER(38)
BYTES NUMBER(38)
OTHER_TAG VARCHAR2(255)
PARTITION_START VARCHAR2(255)
PARTITION_STOP VARCHAR2(255)
PARTITION_ID NUMBER(38)
OTHER LONG
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41. Operating System Dependent Issues
OS block size
Caching issues
And the list goes on …
(make friends with your Sys Admin)
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