Umesh Sharma: 2013

Thursday, September 19, 2013

Oracle DBA sql script

http://www.oracle-base.com/dba/scripts.php

Oracle DBA script

Tuesday, August 20, 2013

Standby Database to Read / Write then again standby Oracle

http://www.idevelopment.info/data/Oracle/DBA_tips/Data_Guard/DG_52.shtml

Standby Database to Read / Write then again standby Oracle

http://www.idevelopment.info/data/Oracle/DBA_tips/Data_Guard/DG_52.shtml

Sunday, August 18, 2013

P & T Oracle Top 10 mistake

Top Ten Mistakes Found in Oracle Systems

This section lists the most common mistakes found in Oracle systems. By following the

Oracle performance improvement methodology, you should be able to avoid these

mistakes altogether. If you find these mistakes in your system, then re-engineer the

application where the performance effort is worthwhile. See "Automatic Performance

Tuning Features" on page 1-5 for information on the features that help diagnose and

tune Oracle systems. See Chapter 10, "Instance Tuning Using Performance Views" for a

discussion on how wait event data reveals symptoms of problems that can be

impacting performance.

1. Bad Connection Management

The application connects and disconnects for each database interaction. This

problem is common with stateless middleware in application servers. It has over

two orders of magnitude impact on performance, and is totally unscalable.

2. Bad Use of Cursors and the Shared Pool

Not using cursors results in repeated parses. If bind variables are not used, then

there is hard parsing of all SQL statements. This has an order of magnitude impact

in performance, and it is totally unscalable. Use cursors with bind variables that

See Also: Oracle Database Reference for more information on

V$SQL and V$SQLSTATS

The Oracle Performance Improvement Method

Performance Improvement Methods 3-5

open the cursor and execute it many times. Be suspicious of applications

generating dynamic SQL.

3. Bad SQL

Bad SQL is SQL that uses more resources than appropriate for the application

requirement. This can be a decision support systems (DSS) query that runs for

more than 24 hours or a query from an online application that takes more than a

minute. SQL that consumes significant system resources should be investigated for

potential improvement. ADDM identifies high load SQL and the SQL tuning

advisor can be used to provide recommendations for improvement. See Chapter 6,

"Automatic Performance Diagnostics" and Chapter 12, "Automatic SQL Tuning".

4. Use of Nonstandard Initialization Parameters

These might have been implemented based on poor advice or incorrect

assumptions. Most systems will give acceptable performance using only the set of

basic parameters. In particular, parameters associated with SPIN_COUNT on

latches and undocumented optimizer features can cause a great deal of problems

that can require considerable investigation.

Likewise, optimizer parameters set in the initialization parameter file can override

proven optimal execution plans. For these reasons, schemas, schema statistics, and

optimizer settings should be managed together as a group to ensure consistency of

performance.

5. Getting Database I/O Wrong

Many sites lay out their databases poorly over the available disks. Other sites

specify the number of disks incorrectly, because they configure disks by disk space

and not I/O bandwidth. See Chapter 8, "I/O Configuration and Design".

6. Redo Log Setup Problems

Many sites run with too few redo logs that are too small. Small redo logs cause

system checkpoints to continuously put a high load on the buffer cache and I/O

system. If there are too few redo logs, then the archive cannot keep up, and the

database will wait for the archive process to catch up. See Chapter 4, "Configuring

a Database for Performance" for information on sizing redo logs for performance.

7. Serialization of data blocks in the buffer cache due to lack of free lists, free list

groups, transaction slots (INITRANS), or shortage of rollback segments.

This is particularly common on INSERT-heavy applications, in applications that

have raised the block size above 8K, or in applications with large numbers of

active users and few rollback segments. Use automatic segment-space

management (ASSM) to and automatic undo management solve this problem.

8. Long Full Table Scans

Friday, August 9, 2013

Oracle Database 11gR2 Metalink Notes

Doc ID 1385682.1 The New My Oracle Support User Interface

Doc ID 1371759.1 How To Migrate A Huge ASM Database From Windows 64 bit To Linux 64 bit With The Minimal Down Time?

Doc ID 413484.1 Data Guard Support for Heterogeneous Primary and Physical Standbys in Same Data Guard Configuration

Doc ID 252219.1 Document TitleSteps To Migrate/Move a Database From Non-ASM to ASM And Vice-Versa

Doc ID 369644.1 Document TitleFrequently Asked Questions about Restoring Or Duplicating Between Different Versions And Platforms

Doc ID 881421.1 Using Active Database Duplication to Create Cross Platform Data Guard Setup (Windows/Linux)

Doc ID 988222.1 Oracle Database 11g Release 2 Information Center

Doc ID 785351.1 Oracle 11gR2 Upgrade Companion

Doc ID 958181.1 Rolling a Standby Forward using an RMAN Incremental Backup To Fix The Nologging Changes

Doc ID 881421.1 Using Active Database Duplication to Create Cross Platform Data Guard Setup (Windows/Linux)

Doc ID 874352.1 RMAN 11GR2 : DUPLICATE WITHOUT CONNECTING TO TARGET DATABASE

Doc ID 805438.1 How To Open Physical Standby For Read Write Testing and Flashback

Doc ID 330535.1 Restore Points in Oracle10g Release2

Doc ID 430221.1 How To Reload Datapump Utility EXPDP/IMPDP

Doc ID 247611.1 Known RMAN Performance Problems

Doc ID 262066.1 How To Size UNDO Tablespace For Automatic Undo Management

Doc ID 311615.1 Oracle 10G new feature – Automatic Undo Retention Tuning

Doc ID 286496.1 Export/Import DataPump Parameter TRACE – How to Diagnose Oracle Data Pump

Doc ID 398838.1 FAQ: SQL Query Performance – Frequently Asked Questions

Doc ID 1232802.1 RAC One — Changes in 11.2.0.2

Doc ID 1312225.1 Things to Consider Before Upgrade to 11.2.0.2 Grid Infrastructure

Doc ID 1267828.1 SYS Password Management with RAC and Data Guard

Doc ID 1276368.1 Complete checklist for out-of-place manual upgrade from 11.2.0.1 to 11.2.0.2

Doc ID 341880.1 How to convert a 32-bit database to 64-bit database on Linux?

Doc ID 1080410.1 How To Upgrade 10.2 Repository to 11.2 In The Same Database Instance

Doc ID 883335.1 How To Downgrade From Database 11.2 To Previous Release

Doc ID 1304939.1 11.2 Data Guard Physical Standby Switchover Best Practices using SQL*Plus

Doc ID 1315926.1 11.2.0.1 to 11.2.0.2 Database Upgrade on Exadata Database Machine

Doc ID 953846.1 Grid Control 10.2.0.5.0 now Supports DB 11.2.0.1.0 as a Target

Doc ID 763386.1 Requirements for Installing Oracle 11gR2 32-bit on SLES 10 (x86)

Doc ID 1139563.1 10.2.0.5.4 Grid Control Patch Set Update (PSU)

Doc ID 556610.1 Script to Collect DB Upgrade/Migrate Diagnostic Information (dbupgdiag.sql)

Doc ID 1276368.1 Complete checklist for out-of-place manual upgrade from 11.2.0.1 to 11.2.0.2

Doc ID 1269321.1 Automatic Degree of Parallelism in 11.2.0.2

Doc ID 727062.1 Configuring and using Calibrate I/O

Doc ID 1279458.1 Exadata Database Machine Reference Guide for Upgrade 11.2.0.1 to 11.2.0.2

Doc ID 837570.1 Complete Checklist for Manual Upgrades to 11gR2

Doc ID 884232.1 11gR2 Install (Non-RAC): Understanding New Changes With All New 11.2 Installer

Doc ID 948061.1 How to Check and Enable/Disable Oracle Binary Options

Doc ID 1069015.1 How to determine enabled/disabled components in an 11.2 software-only installation

Doc ID 883299.1 Oracle 11gR2 Relink New Feature

Doc ID 888934.1 Is it possible to deinstall/remove a specific component from already installed Oracle Database Home using OUI?

Doc ID 942406.1 Customize Enterprise Edition Options under 11.2.0.1 version

Doc ID 1245784.1 Installing Component using Installer from 11.2 ORACLE_HOME Fails with OUI-10150

Doc ID 1267942.1 Installing 11.2.0.X Cman Raises Java Exception Referencing S_dlgcfgnaminglabelsid

Doc ID 1232802.1 RAC One — Changes in 11.2.0.2

Doc ID 810394.1 RAC Assurance Support Team: RAC and Oracle Clusterware Starter Kit and Best Practices (Generic)

Doc ID 250.1 Oracle Support Upgrade Advisors

Doc ID 1152016.1 Master Note For Oracle Database Upgrades and Migrations

Doc ID 1084132.1 Differences Between Enterprise, Standard and Personal Editions on Oracle 11.2

Doc ID 1116484.1 Master Note For Oracle Recovery Manager (RMAN)

Doc ID 1187723.1 Master Note for Automatic Storage Management (ASM)

Doc ID 1050908.1 How to Troubleshoot Grid Infrastructure Startup Issues

Doc ID 274526.1 How To Download And Install OPatch

Doc ID 300062.1 How To Clone An Existing RDBMS Installation Using OUI

Doc ID : 949322.1 Oracle11g Data Guard: Database Rolling Upgrade Shell Script

Doc ID : 300062.1 How To Clone An Existing RDBMS Installation Using OUI

Doc ID : 1101938.1 Master Note for Data Guard

Doc ID 1112983.1 How to Reload the JVM in 11.2.0.x

Doc D : 869084.1 New PL/SQL Features for 11g Release 1 (11.1)

Doc ID : 1092213.1 ASM 11.2 Configuration KIT (ASM 11gR2 Installation & Configuration, Deinstallation, Upgrade, ASM Job Role Separation.

Doc ID : 884522.1 How to Download and Run Oracle’s Database Pre-Upgrade Utility.

Doc ID : 386408.1 What Is The Fastest Way To Cleanly Shutdown An Oracle Database?

Doc ID : 1089476.1 Patch 11gR2 Grid Infrastructure Standalone Server.

Doc ID : 1059516.1 Step by step Installation of 11.1 Grid control

Doc ID : 1086562.1 My Oracle Support is now available through Grid Control 11g

Doc ID : 1076420.1 Upgrade Path to Oracle Enterprise Manager 11g Grid Control Release 1 (11.1.0.1.0) from previous releases (10.1.0.x.0 / 10.2.0.x.0)

Doc ID : 1073647.1 How to check/set the database parameters housing the GC repository before GC Install/upgrade

Doc ID : 605398.1 How to to find the version of the main EM components

Doc ID : 412431.1 Oracle Enterprise Manager 10g Grid Control Certification Checker

Doc ID : 810394.1 RAC Assurance Support Team: RAC and Oracle Clusterware Starter Kit and Best Practices (Generic)

Doc ID : 952302.1 Is Microsoft Windows 7 certified to install/run Oracle Database Server/Client ?

Doc ID : 742060.1 Release Schedule of Current Database Releases

Doc ID : 161818.1 Oracle Database (RDBMS) Releases Support Status Summary

Doc ID : 1060197.1 Self-PacedTraining for Oracle Database 11g Release 2

Doc ID : 988222.1 Oracle Database 11g Release 2 Information Center

Doc ID : 1059163.1 Database Release 11.2 Product Info Center: Planning Information Directory

Doc ID : ID 948187.1 ACFS Technical Overview and Deployment Guide

Doc ID : 950200.1 ASM 11gR2: How To Upgrade An ASM Instance To Release 11gR2 (11.2.0.1.0)?

Doc ID : 1069369.1 How to Delete or Add Resource in 11gR2 Grid Infrastructure

Doc ID : 1063299.1 Tablespace Transport for a Single Partition

Doc ID : 733205.1 Migration of Oracle Database Instances Across OS Platforms

Doc ID : 433472.1 OS Watcher For Windows (OSWFW) User Guide

Doc ID : 1072545.1 RMAN Performance Tuning Using Buffer Memory Parameters

Doc ID : 943567.1 11g new feature: Extended Composite Partitioning (Overview, Example and Use)

Doc ID : 948061.1 How to Check and Enable/Disable Oracle Binary Options

Doc ID : 1056322.1 How to Troubleshoot 11gR2 Installation Issue

Doc ID : 1058646.1 How to integrate a 10g/11gR1 RAC database with 11gR2 clusterware (SCAN)

Doc ID : 1050908.1 How to Troubleshoot Grid Infrastructure Startup Issues

Doc ID : 1058646.1 How to integrate a 10g/11gR1 RAC database with 11gR2 clusterware (SCAN)

Doc ID : 1050908.1 How to Troubleshoot Grid Infrastructure Startup Issues

Doc ID : 1053147.1 11gR2 Clusterware and Grid Home – What You Need to Know

Doc ID : 330358.1 CRS 10gR2/ 11gR1/ 11gR2 Diagnostic Collection Guide

Doc ID : 161818.1 Oracle Database (RDBMS) Releases Support Status Summary

Doc ID : 301137.1 OS Watcher User Guide

Doc ID : 1050693.1 Troubleshooting 11.2 Clusterware Node Evictions (Reboots)

Doc ID : 169706.1 Oracle® Database on Unix AIX®,HP-UX®,Linux®,Mac OS® X,Solaris®,Tru64 Unix® Operating Systems Installation and Configuration Requirements Quick Reference (8.0.5 to 11.2)

Doc ID : 883028.1 New Background Processes introduced by ACFS

Doc ID : 810394.1 RAC Assurance Support Team: RAC Starter Kit and Best Practices (Generic)

Doc ID : 220970.1 RAC: Frequently Asked Questions

Doc ID : 970473.1 Manual installation, deinstallation and verification of Oracle Text 11gR2

Doc ID : 421191.1 Complete checklist for manual upgrades of Oracle databases from anyversion to any version on any platform

Doc ID : 763386.1 Requirements for Installing Oracle 11gR2 32-bit on SLES 10 (x86)

Doc ID : 785351.1 Oracle 11gR2 Upgrade Companion

Doc ID : 837570.1 Complete Checklist for Manual Upgrades to 11gR2

Doc ID : 851598.1 Linux OS Requirements Reference List for Database Server

Doc ID : 870814.1 Complete checklist to upgrade the database to 11gR2 using DBUA

Doc ID : 871665.1 How To Restore The Database To The Source Release After Upgrading The Database To Oracle 11gR2 Using DBUA

Doc ID : 880211.1 Requirements for Installing Oracle 11gR2 RDBMS on RHEL (and OEL) 4 x86

Doc ID : 870877.1 How To Save Oracle Enterprise Manager Database Control Data Before Upgrading The Single Instance Database To Other Release ?

Doc ID : 880936.1 Requirements for Installing Oracle 11gR2 RDBMS on RHEL (and OEL) 5 on 32-bit x86

Doc ID : 881025.1 Requirements for Installing Oracle 11gR2 32-bit on SLES 11 (x86)

Doc ID : 881044.1 Requirements for Installing Oracle 11gR2 64-bit (AMD64/EM64T) on SLES 11

Doc ID : 883299.1 Oracle 11gR2 Relink New Feature

Doc ID : 883335.1 How to downgrade from 11.2 to previous release.

Doc ID : 883743.1 How To Deinstall Oracle Home In 11gR2 ?

Doc ID : 884232.1 11gR2 Install (Non-RAC): Understanding New Changes With All New 11.2 Installer

Doc ID : 884282.1 “Grid infrastructure” is not Grid Control 11gR2 (11.2.0.1.0)

Doc ID : 884435.1 Requirements for Installing Oracle 11gR2 64-bit (AMD64/EM64T) on SLES 10

Doc ID : 886749.1 Oracle 11gR2 Deinstall And Deconfig Tool Options

Doc ID : 886807.1 How To Create A Parameter File For Silent Deinstallation Of Oracle 11gR2

Doc ID : 948040.1 How To Rename A Diskgroup On ASM 11gR2?

Doc ID : 954552.1 11.2 Oracle Restart cannot manage 10.1.x single instances

Doc ID : 886407.1 ACFS/ADVM is NOT started automatically after node reboot or after CRS is restarted in non-RAC environment

Doc ID : 887658.1 Reconfigure HAS and CSS for nonRAC ASM on 11.2

Doc ID : 947520.1 AFTER NODE REBOOT CSSD IS NOT STARTED IN 11gR2 Non-RAC

Doc ID : 942166.1 How to Proceed from Failed 11gR2 Grid Infrastructure (CRS) Installation

Doc ID : 948456.1 Pre-11.2 Database Issues in 11gR2 Grid Infrastructure Environment

Doc ID : 975457.1 How to Troubleshoot Connectivity Issue with 11gR2 SCAN Name

Doc ID : 887962.1 11gR2 New Feature: Deferred Segment Creation

Friday, May 24, 2013

CRSCTL command for RAC Cluster Service

`crs_stat`	`crsctl check cluster -all` `crsctl stat res -t`
`crs_register`	`crsctl add resource` `crsctl add type` `crsctl modify resource` `crsctl modify type`
`crs_unregister`	`crsctl stop resource` `crsctl modify resource` `resource_name` `-attr "AUTO_START=never"`
`crs_start`	`crsctl start resource` `crsctl start crs` `crsctl start cluster`
`crs_stop`	`crsctl stop resource` `crsctl stop crs` `crsctl stop cluster`
`crs_getperm`	`crsctl getperm resource` `crsctl getperm type`
`crs_profile`	`crsctl add resource` `crsctl add type` `crsctl status resource` `crsctl status type` `crsctl modify resource` `crsctl modify type`
`crs_relocate`	`crsctl relocate resource`
`crs_setperm`	`crsctl setperm resource` `crsctl setperm type`
`crsctl check crsd`	`crsctl check crs`
`crsctl check cssd`	`crsctl check css`
`crsctl check evmd`	`crsctl check evm`
`crsctl debug res log` `resource_name:level`	`crsctl set log`
`crsctl set css votedisk`	`crsctl add css votedisk` `crsctl delete css votedisk` `crsctl query css votedisk` `crsctl replace css votedisk`
`crsctl start resources`	`crsctl start resource -all`
`crsctl stop resources`	`crsctl stop resource -all` `http://docs.oracle.com/cd/E11882_01/rac.112/e16794/crsref.htm#autoId61`

Friday, May 3, 2013

Unix IPCS and Oracle Example

http://www.thegeekstuff.com/2010/08/ipcs-command-examples/

Thursday, May 2, 2013

query For No of sql_id execution ans Hash Value in Oracle

set lines 155

col execs for 999,999,999
col avg_etime for 999,999.999
col avg_lio for 999,999,999.9
col begin_interval_time for a30
col node for 99999
break on plan_hash_value on startup_time skip 1

select ss.snap_id, ss.instance_number node, begin_interval_time, sql_id, plan_hash_value,nvl(executions_delta,0) execs,
(elapsed_time_delta/decode(nvl(executions_delta,0),0,1,executions_delta))/1000000 avg_etime,
(buffer_gets_delta/decode(nvl(buffer_gets_delta,0),0,1,executions_delta)) avg_lio
from DBA_HIST_SQLSTAT S, DBA_HIST_SNAPSHOT SS
where sql_id = nvl('&sql_id','gzxwajs4zqpmb')
and ss.snap_id = S.snap_id
and ss.instance_number = S.instance_number
and executions_delta > 0
order by 1, 2, 3
/
select DBMS_SQLTUNE.REPORT_SQL_MONITOR(type=>'HTML',report_level=>'ALL',sql_id=>'gzxwajs4zqpmb') as report FROM dual;

Wednesday, May 1, 2013

SRVCTL Command Help in Oracle

gdcbs320%%=====$CRS_HOME/bin/srvctl -h

Usage: srvctl [-V]

Usage: srvctl add database -d -o [-m ] [-p ] [-A ip>/netmask] [-r {PRIMARY
PHYSICAL_STANDBY
LOGICAL_STANDBY}] [-s ] [-n ] [-y {AUTOMATIC
MANUAL}]

Usage: srvctl add instance -d -i -n

Usage: srvctl add service -d -s -r "" [-a ""] [-P ]

Usage: srvctl add service -d -s -u {-r ""
-a ""}

Usage: srvctl add nodeapps -n -o -A ip>/netmask[/if1[
if2
...]]

Usage: srvctl add asm -n -i -o [-p ]

Usage: srvctl config database

Usage: srvctl config database -d [-a] [-t]

Usage: srvctl config service -d [-s ] [-a] [-S ]

Usage: srvctl config nodeapps -n [-a] [-g] [-o] [-s] [-l]

Usage: srvctl config asm -n

Usage: srvctl config listener -n

Usage: srvctl disable database -d

Usage: srvctl disable instance -d -i ""

Usage: srvctl disable service -d -s "" [-i ]

Usage: srvctl disable asm -n [-i ]

Usage: srvctl enable database -d

Usage: srvctl enable instance -d -i ""

Usage: srvctl enable service -d -s "" [-i ]

Usage: srvctl enable asm -n [-i ]

Usage: srvctl getenv database -d [-t ""]

Usage: srvctl getenv instance -d -i [-t ""]

Usage: srvctl getenv service -d -s [-t ""]

Usage: srvctl getenv nodeapps -n [-t ""]

Usage: srvctl modify database -d [-n ] [-m ] [-p ] [-r {PRIMARY
PHYSICAL_STANDBY
LOGICAL_STANDBY}] [-s ] [-y {AUTOMATIC
MANUAL}]

Usage: srvctl modify instance -d -i -n

Usage: srvctl modify instance -d -i {-s
-r}

Usage: srvctl modify service -d -s -i -t [-f]

Usage: srvctl modify service -d -s -i -r [-f]

Usage: srvctl modify service -d -s -n -i [-a ] [-f]

Usage: srvctl modify asm -n -i [-o ] [-p ]

Usage: srvctl relocate service -d -s -i -t [-f]

Usage: srvctl remove database -d [-f]

Usage: srvctl remove instance -d -i [-f]

Usage: srvctl remove service -d -s [-i ] [-f]

Usage: srvctl remove nodeapps -n "" [-f]

Usage: srvctl remove asm -n [-i ] [-f]

Usage: srvctl setenv database -d {-t =[,=,...]
-T =}

Usage: srvctl setenv instance -d [-i ] {-t "=[,=,...]"
-T "="}

Usage: srvctl setenv service -d [-s ] {-t "=[,=,...]"
-T "="}

Usage: srvctl setenv nodeapps -n {-t "=[,=,...]"
-T "="}

Usage: srvctl start database -d [-o ]

Usage: srvctl start instance -d -i "" [-o ]

Usage: srvctl start service -d [-s "" [-i ]] [-o ]

Usage: srvctl start nodeapps -n

Usage: srvctl start asm -n [-i ] [-o ]

Usage: srvctl start listener -n [-l ]

Usage: srvctl status database -d [-f] [-v] [-S ]

Usage: srvctl status instance -d -i "" [-f] [-v] [-S ]

Usage: srvctl status service -d [-s ""] [-f] [-v] [-S ]

Usage: srvctl status nodeapps -n

Usage: srvctl status asm -n

Usage: srvctl stop database -d [-o ]

Usage: srvctl stop instance -d -i "" [-o ]

Usage: srvctl stop service -d [-s "" [-i ]] [-f]

Usage: srvctl stop nodeapps -n [-r]

Usage: srvctl stop asm -n [-i ] [-o ]

Usage: srvctl stop listener -n [-l ]

Usage: srvctl unsetenv database -d -t ""

Usage: srvctl unsetenv instance -d [-i ] -t ""

Usage: srvctl unsetenv service -d [-s ] -t ""

Usage: srvctl unsetenv nodeapps -n -t ""

Find Session Generating a lot of REDO in Oracle

Archive logs [ID 167492.1]

To find sessions generating lots of redo, you can use either of the following

methods. Both methods examine the amount of undo generated. When a transaction

generates undo, it will automatically generate redo as well.

The methods are:

1) Query V$SESS_IO. This view contains the column BLOCK_CHANGES which indicates

how much blocks have been changed by the session. High values indicate a

session generating lots of redo.

The query you can use is:

SQL> SELECT s.sid, s.serial#, s.username, s.program,

2 i.block_changes

3 FROM v$session s, v$sess_io i

4 WHERE s.sid = i.sid

5 ORDER BY 5 desc, 1, 2, 3, 4;

Run the query multiple times and examine the delta between each occurrence

of BLOCK_CHANGES. Large deltas indicate high redo generation by the session.

2) Query V$TRANSACTION. This view contains information about the amount of

undo blocks and undo records accessed by the transaction (as found in the

USED_UBLK and USED_UREC columns).

The query you can use is:

SQL> SELECT s.sid, s.serial#, s.username, s.program,

2 t.used_ublk, t.used_urec

3 FROM v$session s, v$transaction t

4 WHERE s.taddr = t.addr

5 ORDER BY 5 desc, 6 desc, 1, 2, 3, 4;

Run the query multiple times and examine the delta between each occurrence

of USED_UBLK and USED_UREC. Large deltas indicate high redo generation by

the session.

You use the first query when you need to check for programs generating lots of

redo when these programs activate more than one transaction. The latter query

can be used to find out which particular transactions are generating redo.