Data Guard 的3种数据保护模式

1. 最大保护模式

原理： 当事务提交时，日志必须同时写到Primary数据库和至少一个Standby数据库，以保证Primary和Standby的数据的实时同步。

问题： 1. 影响Primary数据库的性能； 2. 当日志无法同步到至少一个Standby时，Primary会被强制Shutdown。

适用范围： 除非对于数据安全极其敏感的系统，否则很少使用该模式。

2. 最大性能模式（默认）

原理：当Primary的日志无法传递到Standby时，Primary不受影响，且会不断尝试向Standby 传递日志，直至成功。

问题： 无法保证数据的绝对安全，会造成部分数据丢失。

3. 最大可用性模式（折中方案）

原理： 正常情况下，和最大保护模式一样，但当日志无法同步到Standby时，并不会导致Primary的Shutdown，此时，自动切换至最大性能模式；当所有的日志全部传递至Standby时，又切换回最大保护模式。

问题： 1. 比最大性能模式安全，当仍无法保证数据的绝对安全; 2. 对Primary数据库性能也有影响

=============================================

在道富的Data

Guard架构中，大都采用最大性能模式，为了把可能的数据丢失降到最小，部署一Autosys job，该job每隔半小时查询Primary和Standby间的Gap，若Gap超过指定限度，便向oncall DBA发beep。

附录： Standby check job 代码

#!/bin/ksh

#**********************************************************************

# SCCS Information

# ----------------

# Module : dba_oracle_check_standby

# Version : 1.4

# Date Changed : 10/13/09 13:42:33

# Date Retrieved: 10/19/09

# Type :

#**********************************************************************

# Revision History:

#

# Date Name Description

# -------- -------------- ----------------------------------------

# 11/06/07 Alan Stanke Original Development

# 09/16/09 Fei Wu Added "set tab off" in check_dataguard_progress

#

#**********************************************************************

# File Description:

# -----------------

# This script. will monitor the log ship/apply progress on a

# Data Guard Standby instance

#

# This script. must be run locally on the standby machine.

# It will:

# - connect to the standby instance and record the numbers of:

# - the last archived log on the standby

# - the last applied archived log on the standby

# - connect remotely to the primary instance and record the number of:

# - the current log on the primary

# - compare the number of the current log on the primary with the

# the log latest archived log on the primary

# - generate an error if they are too far out of sync (based on

# the log threshold parameter

# - compare the number of the current log on the primary with the

# the log latest applied archived log on the primary

# - generate an error if they are too far out of sync (based on

# the applied log threshold parameter

#

# The parameters are as follows:

# [-s standby instance ] (required)

# [-p primary instance ] (default: same name as standby instance)

# [-t instance thread ] (default: 1)

# [-T log threshold] (default: 1)

# [-A applied log threshold] (default: 2)

#

# Note: For
Oracle

RAC, you will need to run this for each RAC node.

# (i.e. one for each "thread/primary RAC instance")

#

#************************************************************************

#=================================================

sqlplus_function ( ) {

#-------------------------------------------------

sqlplus -s /nolog << EOF

$SQLIN

EOF

RETURN_CODE=$?

}

#=================================================

get_dbmaint_password ( ) {

#-------------------------------------------------

if [ "$env_ind" = "dev" ]

then

#======================

# DEV environment

#----------------------

LD_LIBRARY_PATH=/ssb/cm/security/password/lib:$LD_LIBRARY_PATH; export LD_LIBRARY_PATH

PW_MATRIX=/auto/dba/monitor/.PASSWORD_MATRIX; export PW_MATRIX

# If this is a development Linux machine,

# use /ssb/projects/dba/monitor/.PASSWORD_MATRIX_LINUX matrix file

# (LINUX has a different characters set than Solaris/AIX).

THE_OS=`uname`

if [ "$THE_OS" = "Linux" ]

then

echo "Note: using the LINUX development version of the password matrix "

PW_MATRIX=/auto/dba/monitor/.PASSWORD_MATRIX_LINUX; export PW_MATRIX

fi

PW_DIR=/auto/cm/security/password/exe; export PW_DIR

NEWARG=DB_SERVER_NEW_DEV

else

#======================

# PROD/UAT environment

#----------------------

LD_LIBRARY_PATH=/usr/local/ccms/lib:$LD_LIBRARY_PATH; export LD_LIBRARY_PATH

PW_MATRIX=/usr/local/ccms/security/dat/.DATABASE_MATRIX; export PW_MATRIX

PW_DIR=/usr/local/ccms/security/exe; export PW_DIR

NEWARG=DB_SERVER_NEW

fi

export LD_LIBRARY_PATH

export PW_MATRIX

export PW_DIR

#

# get dbmaint password

#

#NEWPSWD=`${PW_DIR}/pwEcho.exe DB_SERVER_NEW_DEV dbmaint`

#NEWPSWD=`${PW_DIR}/pwEcho.exe DB_SERVER_NEW dbmaint`

NEWPSWD=`${PW_DIR}/pwEcho.exe $NEWARG dbmaint`

rc=$?

if [ "$NEWPSWD" = "NA" ]

then

ERROR_FLAG=y

pswd="NA"

echo " "

echo "***ERROR***ERROR***ERROR*** "

echo "Unable to get the dbmaint password from the password matrix"

echo "exit 99"

echo " "

exit 99

else

pswd=$NEWPSWD

fi

}

#=================================================

check_dataguard_progress( ) {

#-------------------------------------------------

SQLIN=`cat <<EOF

connect / as sysdba;

set feedback off

set heading off

set tab off

select 'ABLE TO CONNECT TO STANDBY' from dual;

select 'STANDBY_LAST_LOG', max(sequence#)

from v\\$archived_log

where thread# = $THREAD ;

select 'STANDBY_LAST_APPLIED_LOG', max(sequence#)

from v\\$archived_log

where applied='YES'

and thread# = $THREAD

group by thread# ;

connect dbmaint/${pswd}@${PRIMARY_INSTANCE} ;

set feedback off

set lin 150

set heading off

set tab off

select 'ABLE TO CONNECT TO PRIMARY' from dual;

select 'PRIMARY_CURRENT_LOG', sequence#

from v\\$log

where status='CURRENT'

and thread# = $THREAD ;

-- commented out following... it may be useful in the future

--select 'PRIMARY_ARCHIVE_DEST_2_STATUS', status, error from v\\$archive_dest where dest_id = 2;

EOF

`

SQLOUT=`sqlplus_function`

# debug

#echo " "

#echo "SQLOUT follows: "

#echo "$SQLOUT"

#echo " "

GREPCOUNT=`echo "$SQLOUT" | grep -c "ORA-"`

if [ "$GREPCOUNT" != "0" ]

then

echo "***ERROR***ERROR***ERROR***"

echo "An ORA-xxx message was encountered in the
SQL output. "

echo "SQL output follows: "

echo "$SQLOUT"

echo "exit 99"

exit 99

fi

GREPCOUNT=`echo "$SQLOUT" | grep -c "ABLE TO CONNECT TO STANDBY"`

if [ "$GREPCOUNT" != "1" ]

then

echo "***ERROR***ERROR***ERROR***"

echo "Unable to connect to the standby instance, exit 3"

echo "SQL output follows: "

echo "$SQLOUT"

exit 3

fi

GREPCOUNT=`echo "$SQLOUT" | grep -c "ABLE TO CONNECT TO PRIMARY"`

if [ "$GREPCOUNT" != "1" ]

then

echo "***ERROR***ERROR***ERROR***"

echo "Unable to connect to the primary instance, exit 3"

echo "SQL output follows: "

echo "$SQLOUT"

exit 3

fi

STANDBY_LAST_LOG=`

echo "$SQLOUT" | \

grep "STANDBY_LAST_LOG" | \

sed "s/ */ /g" | \

cut -d" " -f2

`

if [ "$STANDBY_LAST_LOG" = "NULL" ]

then

echo "***ERROR***ERROR***ERROR***"

echo "The value for the last log number on the standby is NULL"

echo "(Make sure the thread number is valid.) "

echo "SQL output follows: "

echo "$SQLOUT"

echo "exit 98"

exit 98

fi

STANDBY_LAST_APPLIED_LOG=`

echo "$SQLOUT" | \

grep "STANDBY_LAST_APPLIED_LOG" | \

sed "s/ */ /g" | \

cut -d" " -f2

`

PRIMARY_CURRENT_LOG=`

echo "$SQLOUT" | \

grep "PRIMARY_CURRENT_LOG" | \

sed "s/ */ /g" | \

cut -d" " -f2

`

echo " "

echo "PRIMARY_CURRENT_LOG = $PRIMARY_CURRENT_LOG"

echo "STANDBY_LAST_LOG = $STANDBY_LAST_LOG "

echo "STANDBY_LAST_APPLIED_LOG = $STANDBY_LAST_APPLIED_LOG "

echo " "

echo "Comparing last log on standby with the current log on the primary... "

if [ `expr $STANDBY_LAST_LOG + $LOG_THRESHOLD` -ge $PRIMARY_CURRENT_LOG ]

then

echo " PASS: The last log on the standby is "

echo " within $LOG_THRESHOLD of the current log on the primary. "

else

echo " FAIL: The last log on the standby is "

echo " NOT within $LOG_THRESHOLD of the current log on the primary. "

ERROR_FLAG="y"

fi

echo " "

echo "Comparing last applied log on standby with the current log on the primary... "

if [ `expr $STANDBY_LAST_APPLIED_LOG + $APPLIED_LOG_THRESHOLD` -ge $PRIMARY_CURRENT_LOG ]

then

echo " PASS: The last applied log on the standby is "

echo " within $APPLIED_LOG_THRESHOLD of the current log on the primary. "

else

echo " FAIL: The last applied log on the standby is "

echo " NOT within $APPLIED_LOG_THRESHOLD of the current log on the primary. "

ERROR_FLAG="y"

fi

echo " "

if [ "$ERROR_FLAG" = "y" ]

then

echo "***ERROR***ERROR***ERROR***"

echo "See error message(s) above."

echo "exit 97"

echo " "

exit 97

fi

}

#=================================================

display_usage ( ) {

#-------------------------------------------------

cat <<EOF

display_usage: dba_oracle_check_standby

All parameters not correctly passed:

[-s standby instance ] (required)

[-p primary instance ] (default: same name as standby instance)

[-t instance thread ] (default: 1)

[-T log threshold] (default: 1)

[-A applied log threshold] (default: 2)

EOF

exit 1

}

#=====================================================================

#=====================================================================

#=====================================================================

# MAIN LOGIC

#---------------------------------------------------------------------

#---------------------------------------------------------------------

ERROR_FLAG="n"

echo " "

echo "===================================================================="

echo "===================================================================="

echo "===================================================================="

date

echo "dba_oracle_check_standby "

echo " "

#==============

# get options

#--------------

set -- `getopt s:p:T:A:t: $*`

getopt_rc=$?

if [ "$getopt_rc" -ne "0" ]

then

display_usage

fi

while [ $# -gt 0 ]

do

case $1 in

-s )

shift

STANDBY_INSTANCE=$1

shift

;;

-p )

shift

PRIMARY_INSTANCE=$1

shift

;;

-t )

shift

THREAD=$1

shift

;;

-T )

shift

LOG_THRESHOLD=$1

shift

;;

-A )

shift

APPLIED_LOG_THRESHOLD=$1

shift

;;

-- )

shift

break

esac

done

if [ ! "$STANDBY_INSTANCE" ]

then

display_usage

else

ORACLE_SID="$STANDBY_INSTANCE"

export ORACLE_SID

fi

if [ ! "$PRIMARY_INSTANCE" ]

then

PRIMARY_INSTANCE="$ORACLE_SID"

fi

if [ ! "$THREAD" ]

then

THREAD="1"

fi

if [ ! "$LOG_THRESHOLD" ]

then

LOG_THRESHOLD="1"

fi

if [ ! "$APPLIED_LOG_THRESHOLD" ]

then

APPLIED_LOG_THRESHOLD="2"

fi

export THREAD

export LOG_THRESHOLD

export APPLIED_LOG_THRESHOLD

echo "Check Data Guard log ship/apply progress ... "

echo " "

echo "STANDBY_INSTANCE = $STANDBY_INSTANCE "

echo "PRIMARY_INSTANCE = $PRIMARY_INSTANCE"

echo "THREAD = $THREAD "

echo "LOG_THRESHOLD = $LOG_THRESHOLD"

echo "APPLIED_LOG_THRESHOLD = $APPLIED_LOG_THRESHOLD"

echo "--------------------------------------------------------------------"

echo " "

#=================

# set environment

#-----------------

if [ -r /usr/local/ccms/dba_scripts ]

then

PATH=.:$PATH:/usr/local/ccms/dba_scripts; export PATH

else

if [ -r /usr/local/ccms/dba/scripts ]

then

PATH=.:$PATH:/usr/local/ccms/dba/scripts; export PATH

else

PATH=.:$PATH:/ssb/projects/dba/ndi; export PATH

fi

fi

echo "- sourcing dba_get_env_variables "

. dba_get_env_variables

get_dbmaint_password

echo "- calling check_dataguard_progress"

echo " "

check_dataguard_progress

echo " "

date

echo "completed dba_oracle_check_standby "

echo "===================================================================="

echo " "

echo " "

exit 0