Oracle 11gR2 for RAC Users - Session 2_Free Document Search and Download

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Julian Dyke

Independent Consultant

Is RAT Worth Catching?

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Introduction

Real Application Testing (RAT)

Introduced in Oracle 11gR1
Also referred to as Database Replay

This presentation describes RAT in Oracle 11gR2

Separately licenced option .

Processor license *

Real Application Testing $11,500

Some comparative processor license *

Enterprise Edition $47,500
Real Application Clusters $23,000
Partitioning Option $11,500

* Source – Oracle Technology Global Price List – 08Nov12

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Database Replay

Client

Oracle
Database

Storage

Workload
Capture

Production

Test

Workload
Preprocessing

Workload
Replay

Analysis & Reporting

Storage

Application Tier

Oracle
Database

Storage

Replay
Client

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Prerequisites

Workload capture is supported on the following versions:

A one-off patch is required to implement workload capture in versions earlier than 11.2.0.2

Workload replay is supported in 11.2.0.1 and above

Oracle 11.2.0.2 requires one-off patch 11870615

Version

One-off Patch

9.2.0.8

9373986

10.2.0.2

9373986

10.2.0.3

9373986

10.2.0.4

10239989

10.2.0.5

9373986

11.2.0.1

9373986

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Capture User

The workload can be captured by SYS

Alternatively a new user can be created to manage the workload capture. For example:

CREATE USER ratuser
IDENTIFIED BY ratuser
DEFAULT TABLESPACE SYSAUX
TEMPORARY TABLESPACE TEMP
ACCOUNT UNLOCK;

GRANT MGMT_USER TO ratuser;
GRANT EXECUTE_CATALOG_ROLE TO ratuser
GRANT SELECT_CATALOG_ROLE TO ratuser;
GRANT CREATE ANY DIRECTORY TO ratuser;
GRANT DROP ANY DIRECTORY TO ratuser;
GRANT SELECT ON DBA_WORKLOAD_CAPTURES TO RATUSER;

GRANT UNLIMITED TABLESPACE TO ratuser;
GRANT SELECT ANY TABLE TO ratuser;

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Capture Directory

Captured workload is stored in binary files in a directory tree below the capture directory

Capture will stop if capture directory is full

For RAC databases either:

Use a shared file system for workload capture
Use local file systems and subsequently merge contents

For example:

$ mkdir /home/oracle/capture1
$ chmod –R 777 /home/oracle/capture1

sqlplus ratuser/ratuser

SQL> CREATE OR REPLACE DIRECTORY capture1
AS ‘/home/oracle/capture1’;

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Capture Parameters

In Oracle 10.2.0.5 and below, workload capture must be enabled using the PRE_11G_ENABLE_CAPTURE parameter

In Oracle 10.2.0.5 and below:

Workload capture can be enabled using :

$ORACLE_HOME/rdbms/admin/wrrenbl.sql

Workload capture can be disabled using:

$ORACLE_HOME/rdbms/admin/wrrdsbl.sql

Workload capture is enabled by default in Oracle 11.2.0.1 and above

The PRE_11G_ENABLE_CAPTURE parameter is not supported

Workload capture can also be enabled using Enterprise Manager

ALTER SYSTEM SET pre_11g_enable_capture=true SID=‘*’;

ALTER SYSTEM SET pre_11g_enable_capture=false SID=‘*’;

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Starting a Workload Capture

To start a workload capture use the START_CAPTURE procedure:

DBMS_WORKLOAD_CAPTURE.START_CAPTURE
(
name => ‘CAPTURE1’,
dir => ‘CAPTURE1’,
duration => 3600
);

Duration is specified in seconds

1 hour = 3600 seconds
24 hours = 86400 seconds

While capture is enabled a temporary file is created in the capture directory.
For example:

wcr_cap_0003n.start

The file contains 0 bytes and is deleted when the capture is disabled

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RAT Trap - Restart the Database

Oracle recommends that the database is restarted immediately before any workload capture

Ensures that any on-going transactions are completed or rolled back before the capture begins
Reduces amount of divergence

Start workload capture immediately after database restart

Restart database in RESTRICTED mode using STARTUP RESTRICT
Login as SYS and start workload capture
Instance will automatically switch to UNRESTRICTED mode

Experience suggests that the database should be also restarted before any workload replay

Changes to system clock affect AWR snapshots

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RAT Trap – Capture Restrictions

The following types of client request are known restrictions for workload capture

Direct path load of data from external files using utilities such as SQL*Loader
Non-PL/SQL based Advanced Queuing (AQ)
Flashback queries
Oracle Call Interface (OCI) based object navigations
Non SQL-based object access
Distributed transactions

Any distributed transactions that are captured will be replayed as local transactions

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Capture Filters

By default all user sessions are recorded during workload capture

Workload filters can be configured to include or exclude sessions from the capture

Include filters specify user sessions that will be captured. Can be used to capture a subset of the workload

Exclude filters specify user sessions that will not be captured. Can be used to exclude sessions such as

Enterprise Manager Agent,
STATSPACK,
BMC Patrol
Quest Spotlight
Precise I3
etc

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Workload Capture Directories and Files

In Oracle 11.2 and above START_CAPTURE creates subdirectories in capture directory

cap
capfiles

inst1

aa to aj

Each session stores data in a record file e.g. wcr_czq45h0000005.rec

Compressed file
XML-like format with elements and attributes
All SQL calls including

statement text
bind variables
execution time
rows returned
error code

Flushed periodically

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Workload Capture Files

START_CAPTURE generates the following workload metadata (WMD) files automatically in the cap directory

wcr_scapture.wmd - Start capture details
wcr_fcapture.wmd - Finish capture details

In Oracle 11.2 and above START_CAPTURE automatically generates a capture report in the cap directory

wcr_cr.html - Capture report – HTML format
wcr_cr.text - Capture report – Text format

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RAT Trap – Minimum CPU time

A replay requires a minimum of 5 minutes captured CPU time

CPU time NOT Elapsed Time

May be a problem for workloads that are:

I/O-bound
Network intensive
Application-bound

Workload capture period must be long enough to capture five minutes CPU

Can use SLEEP functions to artificially capture CPU

Does not work with PL/SQL DBMS_LOCK.SLEEP function
Works with JServer Java sleep class
Works with External C class

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RAT Trap – Finishing Capture

Capture files are written using buffered I/O

Advantages are:

Lower overhead
Lower impact on workload

Disadvantages are:

Buffers are not flushed automatically
SQL statements can be “lost”

When capture ends or FINISH_CAPTURE is executed:

Timeout period is specified
Sessions will be informed during next database call

If sessions make a database call within timeout period

Capture file buffer will be flushed

Otherwise contents will be lost

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Generating a Capture Report

Determine the capture ID from the capture name e.g.:

SELECT id FROM dba_workload_captures
WHERE name = ‘CAPTURE1’;

ID
1

Generate the capture report e.g.:

SET SERVEROUTPUT ON

DECLARE
l_clob CLOB
BEGIN
l_clob := dbms_workload_capture.report
(
capture_id=>1,
format => DBMS_WORKLOAD_CAPTURE.TYPE_TEXT
);
DBMS_OUTPUT.PUT_LINE (l_clob);
END;
/

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Generating a Capture Report

The capture report format can be:

DBMS_WORKLOAD_CAPTURE.TYPE_TEXT
DBMS_WORKLOAD_CAPTURE.TYPE_HTML

The capture report includes the following:

Details of workload capture including name, filters, date, time and SCN
Overall statistics including total DB time, number of logins, number of transactions
Profile of captured workload
Profile of workload not captured due to version limitations
Profile of uncaptured workload that was excluded by defined filters
Profile of uncaptured workload consisting of background process and scheduled jobs

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Exporting the AWR

An export of the AWR is required for subsequent analysis on the replay system

To export the AWR use the EXPORT_AWR procedure. For example:

BEGIN
dbms_workload_capture.export_awr (capture_id=>1);
END;
/

This creates the following files in the capture directory:

wcr_ca.dmp – Data Pump export
wcr_ca.log – Data Pump log file
wcr_cap_uc_graph.extb – User calls graph

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AWR snapshots are required for subsequent reporting

Ensure that the AWR snapshots are exported before they exceed the AWR retention period and are automatically deleted

RAT Trap – AWR Snapshots

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Restore Strategy

A strategy is required to restore a pre-capture copy of the database to the replay system

One of the following methods can be used:

RMAN backup and restore
RMAN DUPLICATE command
Snapshot standby
Data Pump Import and Export
SAN replication

The database should be restored on the replay system to the point in time at the start of the capture

Recommendation

Enable flashback logging and test the replay before performing a recorded test

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Replay Preparation

Restore pre-capture database to new 10.2.0.4 home

ALTER DATABASE OPEN RESETLOGS;

Modify archive log destination

ALTER SYSTEM SET log_archive_dest_1 =
‘LOCATION=/11/oradata/<DUP_DB>/arch MANDATORY REOPEN=300’;

Run standard 11.2.0.3 upgrade

ALTER SYSTEM SET compatibility = ’11.2.0.3’ SCOPE = SPFILE;

ALTER SYSTEM SET optimizer_features_enable = ’11.2.0.3’ SCOPE = SPFILE;

Update COMPATIBILITY and OPTIMIZER_FEATURES_ENABLE parameters

Ensure replay database parameters have equivalent values to capture database parameters

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Replay User

Replay can be performed by SYS user

Alternatively create a dedicated replay user e.g. RATUSER.

$ sqlplus / as sysdba

SQL> GRANT DBA TO ratuser;

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Replay Directory

The contents of the capture directory should be copied across to the replay server.

It will be necessary to recreate the Oracle directory object:

$ sqlplus ratuser/ratuser

SQL> CREATE OR REPLACE DIRECTORY capture1
AS ‘/home/oracle/capture1’;

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Replay Preprocessing

Pre-process the capture for replay.

For example:

BEGIN
dbms_workload_replay.process_capture
(
capture_dir => ‘CAPTURE1’
);
END;
/

Analyses the workload capture found in the CAPTURE_DIR
Creates workload replay metadata files required to replay the given workload capture

Can be run multiple times on same capture directory
Must be run in same database version as replay
Can run multiple replays following execution of PROCESS_CAPTURE

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Replay Pre-processing

In Oracle 11.2.0.3 the PROCESS_CAPTURE procedure creates a new subdirectory called pp11.2.0.3.0 in the capture directory containing the following files:

wcr_calibrate.html
wcr_commits.extb
wcr_conn_data.extb
wcr_data.extb
wcr_dep_graph.extb
wcr_login.pp
wcr_process.wmd
wcr_references.extb
wcr_scn_order.extb
wcr_seq_data.extb

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Replay Preprocessing

To determine how long pre-processing will take use:

SELECT dbms_workload_replay.process_capture_remaining_time
FROM dual;

Returns an estimate of remaining capture time in minutes

An accurate estimate of remaining processing time cannot be determined during the first minute

Function returns NULL if invoked within first minute of capture pre-processing

To determine what percentage of capture pre-processing is complete use:

SELECT dbms_workload_replay.process_capture_completion
FROM dual;

Returns percentage of capture files that have already been processed
Percentage is updated every 60 seconds

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Workload Analyzer

Workload Analyzer

Available in 11.2.0.2 and above
Java program that analyses a workload capture directory
Identifies parts of captured workload that may not replay accurately e.g.

Insufficient data
Errors occurring during workload capture
Usage features not supported by Database Replay

Results are stored in capture directory in the following files:

wcr_cap_analysis.html
wcr_cap_analysis.xml

Executed automatically by Enterprise Manager during capture pre-processing

Must be invoked manually otherwise

Requires :

$ORACLE_HOME/jdbc/lib/dbranalyzer.jar
$ORACLE_HOME/jdbc/lib/dbrparser.jar
Java 1.5 or above

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Workload Analyzer

Syntax is

java –classpath \
$ORACLE_HOME/jdbc/lib/ojdbc5.jar:\
$ORACLE_HOME/rdbms/jlib/dbrparser.jar:\
$ORACLE_HOME/rdbms/jlib/dbranalyzer.jar \
oracle.dbreplay.workload.checker/CaptureChecker
<capture_directory> <connection_string>

<capture_directory> - operating system path of the capture directory
<connection_string> - connection string of Oracle database (11.1 and above)

e.g. jdbc:oracle:thin:@myhost.mycompany.com:1521:orcl

In Oracle 11.2.0.3 this utility only works with JDBC thin client

JDBC thick client (OCI) fails

Tested successfully with Java 1.6 and ojdbc6.jar

Analyzer will prompt for username/password of database user e.g. ratuser

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RAT Trap - System Clock

Reset the system clock on the replay system to the start time of the capture

Ensure NTP daemon is disabled on replay server

Restart all database instances after resetting the system clock

Consider generating a new ID for the database to ensure AWR snapshots can still be created automatically after the system clock is reset

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RAT Trap – External References

Reconfigure references to external systems to avoid impact on production systems during replay

References that should be resolved include:

Database Links
External Tables
Directory Objects
URLs
E-mail servers

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Initialize Replay

After workload capture has been pre-processed, replay data can be initialized

Loads necessary metadata required by workload replay into tables
captured connection strings are loaded into a table where they can be remapped for replay

For example:

BEGIN
dbms_workload_replay.initialize_replay
(
replay_name => ‘CAPTURE1_REPLAY1’,
replay_dir => ‘CAPTURE1’
);
END;
/

Known to populate the following base tables:

WRR$_REPLAYS
WRR$_CONNECTION_MAP

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Remap Connections

During capture, connection strings used to connect to production system are captured

Connection strings must be remapped to replay system

SELECT
‘EXEC dbms_workload_replay.remap_connection
(‘||a.conn_id||’,’’(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)
(HOST=<replay_server>)(PORT=<port_number>))
(CONNECT_DATA=(SID=<sid>)))’’);’
FROM dba_workload_connection_map a, dba_workload_replays b
WHERE a.replay_id = b.id
AND b.status = ‘INITIALIZED’
ORDER BY a.conn_id;

Note that the TNS address is enclosed by a pair of two single quotes, NOT a pair of double quotes

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RAT Trap – Remap Connections

Ensure that connections are remapped from the capture database to the replay database

If connections are not remapped, workload may be replayed against production database

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Prepare Replay

Specify parameters for workload replay using the PREPARE_REPLAY procedure

For example:

PREPARE_REPLAY parameters include:

SYNCHRONIZATION – Determines how replay will be synchronized. Options are:

SCN – COMMIT order in captured workload is preserved during replay
OBJECT_ID – COMMIT order is maintained for relevant objects only. Relevant objects are objects referenced within current action
OFF – replay is unsynchronized

CONNECT_TIME_SCALE – Scales elapsed time from start of workload capture to time when session connects. Can be used to increase or decrease concurrency. Default is 100%

EXECUTE dbms_workload_replay.prepare_replay (synchronization => TRUE);

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Prepare Replay

PREPARE_REPLAY parameters (continued):

THINK_TIME_SCALE – Scales elapsed time between successive user calls from same session. Default is 100%. If 0 then no delays between user calls

THINK_TIME_AUTO_CORRECT – Automatically correct think time between calls when user calls take longer to complete during replay than capture

SCALE_UP_MULTIPLIER – Defines number of times workload is scaled up during replay

Each captured session will be replayed number of times specified by this parameter
Only one session in each set will execute both queries and updates
Remaining sessions in set will only execute queries

CAPTURE_STS – specifies whether or not to capture a SQL tuning set in parallel with workload replay

STS_CAP_INTERVAL – specifies duration of SQL tuning set capture from cursor cache in seconds

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RAT Trap - Synchronization

Most workloads require full synchronization

Failure to synchronize will increase amount of divergence

Potentially invalidates results

Object synchronization may be useful for a limited range of workloads

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Synchronization

INSERT INTO t
1000000 ROWS

SELECT FROM t
1000000 ROWS

UPDATE t
1000000 ROWS

DELETE FROM t
1000000 ROWS

14:30

14:45

15:00

15:15

15:30

Capture – Table t contains 0 rows at end of capture

Sessions

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Synchronization

INSERT INTO t
1000000 ROWS

SELECT FROM t
0 ROWS

UPDATE t
0 ROWS

DELETE FROM t
0 ROWS

14:30

14:45

15:00

15:15

15:30

Replay without synchronization
In this example table t contains 1000000 rows at end of replay

Sessions

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RAT Trap – Connect and Think Times

Changing connect times and/or think times

Can introduce or alleviate contention
May not be representative of workload

No granularity

Connect / think times must be changed for entire workload
For example cannot distinguish between OLTP and batch within workload

Beware of

Time dependent workload e.g. feeds from other systems
External schedulers e.g. Control M
Application server bottlenecks e.g. Java

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Timing

BATCH

OLTP

14:30

14:45

15:00

15:15

15:30

Sessions

Capture – OLTP sessions run at 14:30 and complete by 14:45
Batch runs at 15:00

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Timing

BATCH

OLTP

14:30

14:45

15:00

15:15

15:30

Sessions

Replay with connect time set to 0%
Batch and OLTP all start at 14:30 – may result in resource contention

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RAT Trap – Scaling

RAT offers limited scaling of workloads

For a specific session

SELECT statements can be scaled to multiple sessions
DML statements are only executed in one session

Therefore scaling can only be considered appropriate for read-only workloads

For all other workloads,

Further analysis will be required
Scaling may not be appropriate

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Workload Replay Client

Replay client is a multi-threaded program called wrc located in $ORACLE_HOME/bin

Included in Oracle 11.2.0.2 and above client

Each thread submits a workload from a captured session

Database will wait for replay clients to connect before replay begins

Replay clients should run on separate hardware to database

Replay clients must have access to replay directory

Replay directory should contain pre-processed workload capture
Replay directory should be in different file system to database files

Replay client must specify username/password

user must have DBA role
user cannot be SYS

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Workload Replay Client - Calibration

Run calibration to determine how many replay clients are required to support the replay workload

For example:

wrc ratuser/ratuser MODE=calibrate REPLAYDIR=‘/home/oracle/capture1’;

Advanced parameters are:

PROCESS_PER_CPU - Maximum number of client process than can be run per CPU (Default: 4)
THREADS_PER_PROCESS - Maximum number of threads than can be run within a client process (Default: 50)

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Workload Replay Client - Calibration

Sample output:

Workload Replay Client: Release 11.2.0.3.0 - Production on Thu May 24 20:01:35 2012

Report for Workload in: /home/oracle/rat/capture31

Recommendation:

Consider using at least 2 clients divided among 1 CPU(s)

You will need at least 135 MB of memory per client process.

If your machine(s) cannot match that number, consider using more clients.

Workload Characteristics:
- max concurrency: 71 sessions
- total number of sessions: 15760

Assumptions:
- 1 client process per 50 concurrent session
- 4 client process per CPU
- 256 KB of memory cache per concurrent session
- think time scale = 100
- connect time scale = 100
- synchronization = TRUE

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Workload Replay Client - Replay

To replay the workload specify the REPLAY mode

For example:

wrc ratuser/ratuser MODE=replay REPLAYDIR=‘/home/oracle/capture1’

Options include:

WORKDIR – directory for trace files
DEBUG – ON or OFF (Default : OFF)
CONNECTION_OVERRIDE – If TRUE the ignore replay connections specified in DBA_WORKLOAD_CONNECTION_MAP. If FALSE (default) use replay connections in DBA_WORKLOAD_CONNECTION_MAP
SERIALIZE_CONNECTS – if TRUE all replay threads will connect to database serially (one after another). Recommended for clients using bequeath protocol. If FALSE (default) replay threads will connect to database concurrently
DSCN_OFF – If TRUE then ignore all dependencies due to block contention during capture when synchronizing replay. If FALSE (default) honour all captured dependencies

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Starting a Workload Replay

After the replay clients have been started, the replay must be started on the database

BEGIN
dbms_workload_replay.start_replay;
END;

The START_REPLAY procedure does not take any arguments

When executed within SQL*Plus,

session returns to the prompt after replay has been started
replay continues to execute in background

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Workload Replay Directories

The replay creates a new replay directory within the capture directory
For example if the capture directory is /home/oracle/rat/capture31:

/home/oracle/rat/capture31/rep930632346

The replay directory name includes the REPLAY_DIR_NUMBER which is reported in DBA_WORKLOAD_REPLAYS

SELECT replay_dir_number
FROM dba_workload_replays
WHERE id = 31;

REPLAY_DIR_NUMBER
930632346

The workload replay creates several files within the replay directory:

wcr_replay.wmd - Replay workload metadata
wcr_rep_uc_graph_930632346.extb - Replay user calls graph
wcr_rr_930632346.xml - Replay report – XML format

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Managing a Workload Replay

To pause a workload replay use:

EXECUTE dbms_workload_replay.pause_replay;

To resume a paused workload replay use:

EXECUTE dbms_workload_replay.resume_replay;

To check if a replay is paused use:

SELECT dbms_workload_replay.is_replay_paused FROM dual;

To cancel a workload replay use:

EXECUTE dbms_workload_replay.cancel_replay;

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Exporting AWR Data

AWR data

can be exported to provide detailed workload analysis
is also required for AWR Compare Period report

To export AWR use the EXPORT_AWR procedure e.g:

EXECUTE dbms_workload_replay.export_awr (replay_id=>107);/

AWR snapshots are required for subsequent reporting

Ensure that the AWR snapshots are exported before they exceed the AWR retention period and are automatically deleted

Replay AWR data is exported into the replay directory, for example:

/home/oracle/rat/capture31/rep930632346

The export files include the REPLAY_DIR_NUMBER:

wcr_ra_930632346.dmp
wcr_ra_930632346.log

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Generating a Replay Report

Identify the most recent replay ID

SELECT MAX(id) AS id FROM dba_workload_replays
WHERE status = 'COMPLETED';

ID
2

Generate the replay report

SET SERVEROUTPUT ON

DECLARE
l_clob CLOB
BEGIN
l_clob := dbms_workload_replay.report
(
replay_id=>1,
format => DBMS_WORKLOAD_REPLAY.TYPE_TEXT
);
DBMS_OUTPUT.PUT_LINE (l_clob);
END;
/

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Generating a Replay Report

The replay report format can be:

DBMS_WORKLOAD_REPLAY.TYPE_TEXT
DBMS_WORKLOAD_REPLAY.TYPE_HTML
DBMS_WORKLOAD_REPLAY.TYPE_XML

The AWR snapshots must still exist in the replay database to generate the replay report

The replay report includes the following:

Details of workload replay including name, filters, date and time
Replay options and number of replay clients started
Overall statistics about the replay and capture including total DB time, number of logins, number of transactions
Profile of replayed workload
Replay divergence
Error divergence
DML and SQL query data divergence

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Divergence

When a workload is replayed there can be divergence between the capture and the replay

There are two types of divergence

Performance Divergence – occurs when changes on the replay system affect overall performance. Changes may include

Software
Hardware
Parameters

Data Divergence – occurs when results of DML or SQL queries do not match

For example a SELECT statement may return fewer rows during replay than during capture

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Listing Divergences

Divergences are reported in DBA_WORKLOAD_REPLAY_DIVERGENCE

Each divergence is identified by

REPLAY_ID
STREAM_ID
CALL_COUNTER

Information about a divergence is reported by the GET_DIVERGING_STATEMENT procedure in DBMS_WORKLOAD_REPLAY

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RAT Trap – PLSQL Blocks

Anonymous PL/SQL blocks are captured

PL/SQL calls within those blocks are not captured
SQL statement calls within those blocks are not captured

Only errors returned by PL/SQL block exceptions are recorded

If recursive exceptions are caught and handled internally these will not be reported

If PL/SQL logic is different, this may not be captured

Replay may be affected by

Changes in supplied PL/SQL packages
Changes in application PL/SQL packages

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Replay Analysis

The following types of reports are available to analyse workload capture and replay:

Capture Report

Replay Report

Compare Period Report

Compare SQLSET report

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Importing a Capture AWR

Before running the compare reports, it is necessary to import the capture AWR

The workload analyzer attempts to import the capture AWR, but this version does not appear to be usable

The capture AWR should be imported into a new schema.

In this example the new schema is called CAPTURE31
RESOURCE role appears to be necessary and sufficient

CREATE USER capture31 IDENTIFIED BY capture31;

GRANT RESOURCE TO capture31;

Identify the ID of the capture workload

SELECT id FROM dba_workload_captures
WHERE name = ‘CAPTURE31’;

ID
115

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Importing a Capture AWR

Import the AWR using the IMPORT_AWR procedure. For example:

SET SERVEROUTPUT ON

DECLARE
l_dbid NUMBER;
BEGIN
l_dbid := dbms_workload_capture.import_awr
(
capture_id => 115,
staging_schema => 'CAPTURE31‘
);

dbms_output.put_line (‘DBID = '||l_dbid);
END;
/

DBID = 2128266044

The IMPORT_AWR function returns the new DBID assigned to the imported AWR.

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Compare Period Reports

Compare Period reports allow comparison of

Workload replay with workload capture
Workload replay with another workload replay from same capture

Only workload replays containing at least 5 minutes of database time can be compared using this report

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Compare Period Reports

For example:

SET PAGESIZE 0
SET TRIMSPOOL ON
SET LINESIZE 500
SET FEEDBACK OFF
SET LONG 1000000
SET SERVEROUTPUT ON

VAR v_clob CLOB

BEGIN
dbms_workload_replay.compare_period_report
(
  replay_id1 => 31,
  replay_id2 => NULL,
  format => DBMS_WORKLOAD_REPLAY.TYPE_HTML,
  result => :v_clob
);

END;
/

PRINT v_clob

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RAT Trap – DB Time

DB time is the best and possibly only metric to compare captures with replays

Other metrics can be used to compare replays with each other

DB time may be affected by

Changes in hardware e.g.

SSD ,
10GbE networks
faster CPU
more memory

Changes in Oracle version

Additional functionality
Longer code paths

Background workload
Divergence

Make sure you understand all the differences between environments before making a decision based on Database Replay outcomes

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Compare SQLSET Reports

SQL Performance Analyzer (SPA) reports can be generated using the DBMS_WORKLOAD_REPLAY package

The SPA can be used to compare

a SQL tuning set from a workload replay with the SQL tuning set from the workload capture
a SQL tuning set from a workload replay with the SQL tuning set from another workload replay from the same workload capture

juliandyke.com

Compare SQLSET Report

SET PAGESIZE 0
SET TRIMSPOOL ON
SET LINESIZE 500
SET FEEDBACK OFF
SET LONG 1000000

VAR v_clob CLOB

DECLARE
l_result VARCHAR2(200);
BEGIN
l_result := dbms_workload_replay.compare_sqlset_report
(
  replay_id1 => 44,
  replay_id2 => NULL,
  format => DBMS_WORKLOAD_REPLAY.TYPE_HTML,
  result => :v_clob
);
END;
/

PRINT v_clob
SPOOL OFF

Compare replay with
original capture

juliandyke.com

Compare SQLSET Report

SET PAGESIZE 0
SET TRIMSPOOL ON
SET LINESIZE 500
SET FEEDBACK OFF
SET LONG 1000000

VAR v_clob CLOB

DECLARE
l_result VARCHAR2(200);
BEGIN
l_result := dbms_workload_replay.compare_sqlset_report
(
  replay_id1 => 44,
  replay_id2 => 42,
  format => DBMS_WORKLOAD_REPLAY.TYPE_HTML,
  result => :v_clob
);
END;
/

PRINT v_clob
SPOOL OFF

Compare replay with
another replay

juliandyke.com

Conclusions

RAT can be very good at capturing and replaying workloads

Requires a lot of user discipline

Follow the capture and replay recommendations

Unsupported workload features can increase divergence

For best results avoid using “enhancements” such as

Object synchronization
Connect time modifications
Think time modifications
Workload scaling

juliandyke.com

Acknowledgements

This presentation would not have been possible without the help of:

Andrew Ashworth (Ash)
Pete Taylor

Thank you

Oracle 11gR2 for RAC Users - Session 2

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