|
| Data Guard is a technology
built into Enterprise Edition. It is not a download or an add-on and
with the excpetion of Active Data Guard fully included, as of this
writing, in the basic EE license. |
The
following was posted by DG Product Manager Larry Carpenter to the OTN
forums on 1-Jun-2010. A small amount of editing has been done for
consistency.
Maximum Protection and Maximum Availability are Data Guard's Zero
Data Loss protection modes.
The only difference is that in Maximum Protection Data Guard will
abort the Primary (not allowing a transaction to be reported as
committed to the application) if the redo cannot be written to a SYNC
standby.
In Maximum Availability it is allowed for a transaction to be
committed even if there are no SYNC standby destinations available. That
would be the 1st failure, the standby is not reachable.
So when the Primary failed after that (the 2nd failure) you would
of course lose data, the data that was generated while the standby was
not reachable before the Primary failed.
However, this is not your situation. What you are experiencing is a misunderstanding of how the databases work.
In Oracle Versions prior to 11.2 the SYNC redo transport works as follows.
1. User says COMMIT.
2. LGWR writes the redo to the Online Redo Log.
3. The LNS processes grabs the same redo from the Log Buffer AFTER
the LGWR has written the redo to the Online redo log file, and sends it
to their standby.
4. When the SYNC standbys all report back that the redo has been
received and written to the standby redo log file OR they fail to
respond within NET_TIMEOUT seconds is the client told that the
transaction has in fact committed.
What you are experiencing is the failure is happening between step
2 and step 3.
The redo is written to the online redo log file at the primary but
the client has not been told that the transaction has actually
committed.
When you failover and do the select count(*) from the Primary you
have the exact count of transactions that the client was actually told
had been committed.
When you then restarted the Primary what does it do? Crash
recovery!
Which will recover the redo that was actually written to the
online redo log file which is that 'last' row which was the current
transaction but was never actually 'committed' to the application.
Your did not actually lose that row as the application was never
told that it was committed.
In a real situation you would have failed over and then when the
Primary came back you would have reinstated it as a standby and not
opened it.
Try your test where your test application prints out the counter
AFTER the commit has finished and then pull the plug, failover and see
if the count in the table on the standby matches the counter in the
application.
Final result, you didn't lose any data that the application was told was committed.
Larry
P.S. As of 11.2 the write to the Online Redo Log file by the LGWR
and the send to the SYNC standby happens in parallel so you will see
even less of what you saw when you try your test in the same way in
11.2) |
| Acronyms |
| Acronym |
Short For |
| ARC0 |
Archiver Process on Local Server |
| ARCH |
Archiver |
| ASYNC |
Asynchronous |
| DMON |
Data Guard Monitor |
| DR |
Disaster Recovery |
| FAL |
Fetch Archive Log |
| LCR |
Logical Change Record |
| LGWR |
Logwriter |
| LNS |
Network Server Process |
| LSP |
Logical Standby Process (SQL Apply for Logical DG) |
| MRP |
Managed Recovery Process (Redo Apply for Physical DG) |
| RFS |
Remote File Server |
| SYNC |
Synchronous |
| TAF |
Transparent Application Failover |
|
| Data Dictionary Objects for Physical DataGuard |
| DBA_LOG_GROUPS |
DBA_HIST_LOG |
GV$MANAGED_STANDBY |
| DBA_LOG_GROUP_COLUMNS |
GV$DATAGUARD_CONFIG |
V$DATABASE |
| DBA_REGISTERED_ARCHIVED_LOG |
GV$DATAGUARD_STATUS |
V$STANDBY_EVENT_HISTOGRAM |
|
| Data Dictionary Objects for Logical DataGuard |
| DBA_LOGSTDBY_EVENTS |
DBA_LOGSTDBY_SKIP |
GV$DATAGUARD_CONFIG |
| DBA_LOGSTDBY_HISTORY |
DBA_LOGSTDBY_SKIP_TRANSACTION |
GV$DATAGUARD_STATS |
| DBA_LOGSTDBY_LOG |
DBA_LOGSTDBY_UNSUPPORTED |
GV$DATAGUARD_STATUS |
| DBA_LOGSTDBY_NOT_UNIQUE |
DBMS_DRS |
GV$LOGSTDBY |
| DBA_LOGSTDBY_PARAMETERS |
DBMS_LOGSTDBY |
GV$LOGSTDBY_STATS |
| DBA_LOGSTDBY_PROGRESS |
GV$ARCHIVE_GAP |
GV$STANDBY_LOG |
|
| Docs |
|
| |
| Data Guard Broker |
| Start Data Guard Manager |
$ DGMGRL |
| Add a standby database to the broker configuration |
ADD DATABASE <database_name> [as connect identifier is <connect-identifier>]; |
| DGMGRL> add database proda; |
| Connect to the database via the broker |
CONNECT username[@connect-identifier] |
DGMGRL> connect sys/syspwd
Connected.
Error:
ORA-16525: the Data Guard broker is not yet available
ORA-06512: at SYS:DBMS_DRS", line 124
ORA-06512: at line 1
SQL> ALTER SYSTEM SET dg_broker_start = TRUE;
System altered.
DGMGRL> connect sys/syspwd
Connected.
DGMGRL> exit
SQL> alter system set DG_BROKER_START = FALSE; |
| Convert or revert a standby between physical and snapshot |
CONVERT <db_unique_name> TO <SNAPSHOT | PHYSICAL> STANDBY; |
| DGMGRL> CONVERT DATABASE prodb TO snapshot standby; |
| Create a broker configuration |
CREATE CONFIGURATION <configuration-name> AS
PRIMARY DATABASE IS <database-name>
CONNECT IDENTIFIER IS <connect-identifier>; |
DGMGRL> CREATE CONFIGURATION 'dg_prod_cfg' AS
PRIMARY DATABASE IS 'proda'
CONNECT IDENTIFIER IS proda.mlib.com; |
| Disable a configuration |
DISABLE CONFIGURATION; |
| DGMGRL> DISABLE CONFIGURATION; |
| Disable a database |
DISABLE DATABASE <database-name>; |
| DGMGRL> DISABLE DATABASE prodb; |
| Disable Fast-Start Failover |
DISABLE FAST_START FAILOVER [FORCE]; |
| DGMGRL> DISABLE FAST_START FAILOVER FORCE; |
| Disable Fast-Start Failover Condition |
DISABLE FAST_START FAILOVER CONDITION <value>; |
| DGMGRL> DISABLE FAST_START FAILOVER CONDITION "corrupted controlfile"; |
| Edit a configuration property |
EDIT CONFIGURATION SET PROPERTY <property_name> = <value>; |
DGMGRL> EDIT CONFIGURATION SET PROPERTY FastStartFailoverThreshold=60;
DGMGRL> EDIT DATABASE 'site1_edrsr8p1' SET PROPERTY 'LogXptMode'='SYNC'; |
| Edit configuration (protection mode) |
EDIT CONFIGURATION SET PROTECTION MODE AS <MAXPROTECTION | MAXAVAILABILITY | MAXPERFORMANCE>; |
| DGMGRL> EDIT CONFIGURATION SET PROTECTION MODE AS MAXAVAILABILITY; |
| Edit database property |
EDIT DATABASE <database-name> SET PROPERTY=<value>; |
| DGMGRL> EDIT DATABASE prodb SET PROPERTY='ArchiveLagTarget'=900; |
| Edit database rename |
EDIT DATABASE <database-name> RENAME TO =<new-database-name>; |
DGMGRL> DISABLE DATABASE prodb;
DGMGRL> EDIT DATABASE prodb RENAME TO='prodc';
DGMGRL> ENABLE DATABASE prodc; |
| Edit database state |
EDIT DATABASE <database-name> SET STATE=<database state>
[WITH APPLY INSTANCE=<instance-name>];
| Database State |
| APPLY-OFF (physical or logical standby database only) |
| APPLY-ON (physical or logical standby database only) |
| TRANSPORT-OFF (primary database only) |
| TRANSPORT-ON (primary database only) |
|
| DGMGRL> EDIT DATABASE prodb SET STATE=apply-off; |
| Edit Instance |
EDIT INSTANCE <instance-name> [ON DATABASE <database-name>]
SET auto pfile=<initialization-file | off>; |
DGMGRL> EDIT INSTANCE 'prodb' ON DATABASE 'prodb' SET AUTO PFILE='initprodb.ora';
DGMGRL> EDIT INSTANCE 'prodb' ON DATABASE 'prodb'
SET PROPERTY 'StandbyArchiveLocation'='/u03/prodb/arch/'; |
| Enable Configuration |
ENABLE CONFIGURATION; |
| DGMGRL> ENABLE CONFIGURATION; |
| Enable Database |
ENABLE DATABASE <database-name>; |
| DGMGRL> ENABLE DATABASE prodb; |
| Enable Fast_Start Failover |
ENABLE FAST_START FAILOVER; |
| DGMGRL> ENABLE FAST_START FAILOVER; |
| Enable Fast_Start Failover Condition |
ENABLE FAST_START FAILOVER CONDITION <value>;
| Fast_Start Failover Conditions |
| Corrupted Controlfile |
Corrupted controlfile |
| Corrupted Dictionary |
Dictionary corruption of a critical database object |
| Datafile Offline |
Data file offline due to a write error |
| Inaccessible Logfile |
LGWR is unable to write to any member of a log group due to an I/O error |
| Stuck Archiver |
Archiver is unable to archive a redo log because device is full or unavailable |
|
| DGMGRL> ENABLE FAST_START FAILOVER CONDITION "Corrupted Dictionary"; |
| Exit the Data Guard Manager program |
EXIT; |
| DGMGRL> EXIT; |
| Change a standby database to be the primary database |
FAILOVER TO <database-name> [IMMEDIATE]; |
| DGMGRL>FAILOVER TO prodb IMMEDIATE; |
| Display description and syntax for a command |
HELP; |
DGMGRL> HELP;
DGMGRL> HELP SHOW; |
| Exit the program |
QUIT; |
| DGMGRL> QUIT; |
| Change a disabled database into a viable standby database |
REINSTATE DATABASE <database_name>; |
| DGMGRL>REINSTATE DATABASE prodb; |
| Comment (remark) to be ignored by DGMGRL |
rem <remark_string>; |
| DGMGRL>REM 'this is a comment'; |
| Removes config info, including all DB profiles and terminates management of all of associated databases |
REMOVE CONFIGURATION [PRESERVE DESTINATIONS]; |
DGMGRL> SHOW CONFIGURATION;
DGMGRL> REMOVE CONFIGURATION PRESERVE DESTINATIONS;
DGMGRL> SHOW CONFIGURATION; |
| Removes the specified standby
database's profile from the broker configuration and terminates broker
management of the standby database |
REMOVE DATABASE <database_name> [PRESERVE DESTINATIONS]; |
| DGMGRL> REMOVE DATABASE proda PRESERVE DESTINATIONS; |
| Removes the specified standby
database's profile from the broker configuration and terminates broker
management of the standby database |
REMOVE INSTANCE <instance-name> [ON DATABASE <database-name>]; |
DGMGRL> SHOW CONFIGURATION;
DGMGRL> REMOVE INSTANCE proda ON DATABASE proda;
DGMGRL> SHOW CONFIGURATION; |
| Display information about a configuration, database, and/or instance |
SHOW CONFIGURATION [VERBOSE | <property_name>]; |
| DGMGRL> SHOW CONFIGURATION VERBOSE; |
| Display information about a database |
SHOW DATABASE [VERBOSE] <database-name> [<property-name>]; |
| DGMGRL> SHOW DATABASE VERBOSE; |
| Display information about a fast_start failover configuration |
SHOW FAST_START FAILOVER; |
| DGMGRL> SHOW FAST_START FAILOVER; |
| Display information about an instance |
SHOW INSTANCE [VERBOSE] <instance-name> [ON DATABASE <database-name>]; |
| DGMGRL> SHOW INSTANCE VERBOSE; |
| Shutdown a currently running Oracle instance |
SHUTDOWN [<ABORT | IMMEDIATE | NORMAL>]; |
| DGMGRL> SHUTDOWN IMMEDIATE; |
| Start Fast-Start Failover observer |
START OBSERVER [FILE=observer_configuration_filename]; |
| DGMGRL> START OBSERVER '/u01/oracle/admin/orabase/dgbroker/orabase_dgcfg'; |
| Start an Oracle database instance |
STARTUP [FORCE] [RESTRICT] [PFILE=<filename>]
[<MOUNT | NOMOUNT | OPEN <READ ONLY | READ WRITE>>]; |
| DGMGRL> STARTUP; |
| Stop the Fast_Start Failover Observer |
STOP OBSERVER; |
| DGMGRL> STOP OBSERVER; |
| Switch roles between the primary database and a standby database |
SWITCHOVER TO <database-name>; |
| DGMGRL> SWITCHOVER TO prodc; |
| |
| Grid Infrastructure Data Guard |
| Role Swap On Physical Standby |
srvctl modify database -d <physStandby> -s open -r primary |
| srvctl modify database -d TSTC -s open -r primary |
| Role Swap On Primary |
srvctl modify database -d <Primary> -s mount -r physical_standby |
| srvctl modify database -d TSTA -s open -r physical_standby |
| |
| 12cR1 New Features |
| Far Sync |
A Data Guard Far Sync instance is a remote Data Guard destination that accepts redo from the primary database
and then ships that redo to other members of the Data Guard configuration.
Manages a control file, receives redo into standby redo logs (SRLs), and archives those SRLs to local archived redo logs.
A Far Sync instance does not have user data files, cannot be
opened for access, cannot run redo apply, and can never function in the
primary role or be converted to any type of standby database.
Far Sync instances are part of the Active Data Guard Far Sync feature, which requires an Active Data Guard license. |
| TBD |
| FastSync |
LOG_ARCHIVE_DEST_n attributes SYNC and NOAFFIRM can be used together enabling a synchronous standby to be
deployed at a futher distance from the primary site. |
| TBD |
| |
| Operating System Installation |
| As root: Create DBA Group and Oracle User (both servers) |
$ /usr/sbin/groupadd oinstall
$ /usr/sbin/groupadd dba
$ /usr/sbin/useradd -m -g oinstall -G dba oracle
$id oracle
$passwd oracle
-- set the password to oracle1
$ id nobody
-- if nobody does not exist then
$ /usr/sbin/useradd nobody |
| As root: Create Installation Directories (both servers) |
mkdir -p /app/oracle
chown -R oracle:dba /app/oracle
chmod -R 775 /app/oracle
mkdir /stage
chown -R oracle:dba /stage |
As root: Alter Kernel Parameters in sysctl.conf by appending the highlighted text
(both servers) |
cd /etc
vi sysctl.conf
fs.file-max = 65536
kernel.shmall = 2097152
kernel.shmmax = 2147483648
kernel.shmmni = 4096
kernel.sem = 250 32000 100 128
# send receive buffers
net.core.rmem_default = 4194304
net.core.rmem_max = 4194304
net.core.wmem_default = 8388608
net.core.wmem_max = 8388608
# tcp read and write buffers
net.ipv4.tcp_rmem=4096 262144 8388608
net.ipv4.tcp_wmem=4096 262144 8388608
net.ipv4.ip_forward = 0
net.ipv4.conf.default.rp_filter = 1
net.ipv4.ip_local_port_range = 1024 65000 |
-- activate changes
/sbin/sysctl -p |
As root: Set Shell Limits
(both servers) |
cd /etc/security
-- modify limits.conf
cat >> /etc/security/limits.conf <<EOF
oracle soft nproc 2047
oracle hard nproc 16384
oracle soft nofile 1024
oracle hard nofile 65536
EOF |
-- modify /etc/pam.d/ login
-- read the file and place above the last lines as indicated
session required /lib/security/pam_limits.so
session required pam_limits.so |
|
As root: Change Default Profile
(both servers) |
cd /etc
-- if Bourne, Korn or Bash shell
cat >> /etc/profile <<EOF
if [ \$USER = "oracle" ]; then
if [ \$SHELL = "/bin/ksh" ]; then
ulimit -p 16384
ulimit -n 65536
else
ulimit -u 16384 -n 65536
fi
umask 022
fi
EOF |
|
As root: Append servers to hosts file
(both servers) |
cd /etc
Note: the line: 127.0.0.1
omega#.mlib.org omega# localhost.localadmin localhost must remain.
If you delete it ... nothing will work properly
vi hosts
| 192.168.1.101 |
omega1 |
omega1.mlib.org |
| 192.168.1.102 |
omega2 |
omega2.mlib.org |
| 10.0.1.1 |
dgomega1 |
dgomega1.mlib.org |
| 10.0.1.2 |
dgomega2 |
dgomega2.mlib.org |
| 192.168.10.01 |
omega1st |
omega1st.mlib.org |
| 192.168.10.02 |
omega2st |
omega2st.mlib.org |
| 192.168.10.100 |
netapp |
netapp.mlib.org |
| 192.168.1.119 |
bigdog |
bigdog.mlib.org |
-- ping all hosts (substitute actual node names for the "omega")
ping 192.168.1.1
ping www.oracle.com
ping omega1
ping omega2
ping omega1.mlib.org
ping omega2.mlib.org |
| Modify .bashrc (both servers) |
cd /home/oracle
vi .bashrc
umask 022
ORACLE_BASE=/app/oracle/product
ORACLE_HOME=/app/oracle/product/11.2.0/dbhome_1
# ORACLE_SID=proda
# ORACLE_SID=prodb
PATH=$ORACLE_HOME/bin:$PATH
export PATH ORACLE_BASE ORACLE_HOME ORACLE_SID
-- sid name on omega1 is proda
-- sid name on omega2 is prodb |
| initproda.ora |
proda.__db_cache_size=687865856
proda.__java_pool_size=16777216
proda.__large_pool_size=16777216
proda.__oracle_base='/app/oracle/product'
proda.__pga_aggregate_target=671088640
proda.__sga_target=989855744
proda.__shared_io_pool_size=0
proda.__shared_pool_size=251658240
proda.__streams_pool_size=0
*.audit_file_dest='/app/oracle/product/admin/proda/adump'
*.audit_trail='db'
*.compatible='11.1.0.0.0'
*.control_files= '/app/oracle/product/oradata/proda/control01.ctl', '/app/oracle/product/oradata/proda/control02.ctl',
'/app/oracle/product/oradata/proda/control03.ctl'
*.db_block_size=8192
*.db_domain=''
*.db_name='proda'
*.db_recovery_file_dest='/app/oracle/product/fast_recovery_area'
*.db_recovery_file_dest_size=2147483648
*.diagnostic_dest='/app/oracle/product'
*.dispatchers='(PROTOCOL=TCP) (SERVICE=prodaXDB)'
*.memory_target=1658847232
*.open_cursors=300
*.processes=150
*.remote_login_passwordfile='EXCLUSIVE'
*.undo_tablespace='UNDOTBS1'
ifile=?/dbs/proda_dg.ora |
| initprodb.ora |
prodb.__db_cache_size=687865856
prodb.__java_pool_size=16777216
prodb.__large_pool_size=16777216
prodb.__oracle_base='/app/oracle/product'
prodb.__pga_aggregate_target=671088640
prodb.__sga_target=989855744
prodb.__shared_io_pool_size=0
prodb.__shared_pool_size=251658240
prodb.__streams_pool_size=0
*.audit_file_dest='/app/oracle/product/admin/proda/adump'
*.audit_trail='db'
*.compatible='11.1.0.0.0'
*.control_files='/app/oracle/product/oradata/proda/control01.ctl',
'/app/oracle/product/oradata/proda/control02.ctl',
'/app/oracle/product/oradata/proda/control03.ctl'
*.db_block_size=8192
*.db_domain=''
*.db_name='proda'
*.db_recovery_file_dest='/app/oracle/product/fast_recovery_area'
*.db_recovery_file_dest_size=2147483648
*.diagnostic_dest='/app/oracle/product'
*.dispatchers='(PROTOCOL=TCP) (SERVICE=prodbXDB)'
*.memory_target=1658847232
*.open_cursors=300
*.processes=150
*.remote_login_passwordfile='EXCLUSIVE'
*.undo_tablespace='UNDOTBS1'
ifile=?/dbs/prodb_dg.ora |
| On omega1 create a password file |
$ cd $ORACLE_HOME/dbs
$ ls -la
orapwd file=orapwproda password=oracle1 ignorecase=y
set linesize 121
col name format a30
col value format a50
SELECT name, value
FROM gv$parameter
WHERE name LIKE '%remote_login%'; |
| On omega2 create a password file |
$ cd $ORACLE_HOME/dbs
$ ls -la
orapwd file=orapwprodb password=oracle1 ignorecase=y
set linesize 121
col name format a30
col value format a50
SELECT name, value
FROM gv$parameter
WHERE name LIKE '%remote_login%'; |
| omega1: listener.ora |
-- Note: SDU needs to be a multiple of MTU
# /sbin/ifconfig
# listener.ora Network Configuration File: /app/oracle/product/11.2.0/dbhome_1/network/admin/listener.ora
# Generated by Oracle configuration tools.
DG_LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.#.1)(PORT = 1526))
(SEND_BUF_SIZE=9375000)
(RECV_BUF_SIZE=9375000))
)
)
SID_LIST_DG_LISTENER =
(SID_LIST =
(SID_DESC =
(SDU = 32767)
(GLOBAL_DBNAME = proda)
(ORACLE_HOME = /app/oracle/product/11.2.0/dbhome_1)
(SID_NAME = proda)
)
)
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = omega1.mlib.org)(PORT = 1521))
)
)
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = /app/oracle/product/11.2.0/dbhome_1)
(PROGRAM = extproc)
)
) |
| omega2: listener.ora |
# listener.ora Network Configuration File: /app/oracle/product/11.2.0/dbhome_1/network/admin/listener.ora
# Generated by Oracle configuration tools.
DG_LISTENER =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.#.2)(PORT = 1526)
(SEND_BUF_SIZE=9375000)
(RECV_BUF_SIZE=9375000))
)
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = /app/oracle/product/11.2.0/dbhome_1)
(PROGRAM = extproc)
)
)
SID_LIST_DG_LISTENER =
(SID_LIST =
(SID_DESC =
(SDU=32767)
(GLOBAL_DBNAME = prodb)
(ORACLE_HOME = /app/oracle/product/11.1.0/dbhome_1)
(SID_NAME = prodb)
)
)
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = omega2.mlib.org)(PORT = 1521))
)
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC0))
)
) |
| both servers: sqlnet.ora |
NAMES.DIRECTORY_PATH= (TNSNAMES, EZCONNECT)
DEFAULT_SDU_SIZE=32767 |
| both servers: tnsnames.ora |
# tnsnames.ora Network Configuration File: /app/oracle/product/11.2.0/dbhome_1/network/admin/tnsnames.ora
# Generated by Oracle configuration tools.
DGLOGSHIPB =
(DESCRIPTION =
(SDU = 32767)
(SEND_BUF_SIZE=9375000)
(RECV_BUF_SIZE=9375000)
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.#.2)(PORT = 1526))
)
(CONNECT_DATA =
(SERVICE_NAME = prodb)
)
)
DGLOGSHIPA =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 10.0.#.1)(PORT = 1526))
)
(CONNECT_DATA =
(SERVICE_NAME = proda)
)
)
PRODB =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = omega2.mlib.org)(PORT =1521))
)
(CONNECT_DATA =
(SERVICE_NAME = prodb)
)
)
PRODA =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = omega1.mlib.org)(PORT =1521))
)
(CONNECT_DATA =
(SERVICE_NAME = proda)
)
)
REPOS =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.119)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = repos)
)
) |
| |
| Physical Data Guard |
dg_proda.ora
Note: Set net_timeout between 10-30 sec. |
remote_login_passwordfile='EXCLUSIVE'
# set max_processes equal to max_connections + 1 for local
log_archive_max_processes=4
log_archive_config='DG_CONFIG=(proda,prodb)'
db_unique_name='proda'
# db_name='proda'
# service_names='proda'
fal_client=proda
fal_server=prodb
standby_file_management='auto'
log_file_name_convert=' ',' '
log_archive_dest_1='LOCATION=/app/oracle/product/fast_recovery_area/arch
valid_for=(all_logfiles,all_roles) db_unique_name=proda'
log_archive_dest_2='service=dglogshipb valid_for=(online_logfile,primary_role) db_unique_name=prodb NET_TIMEOUT=15 REOPEN=60 OPTIONAL MAX_CONNECTIONS=3'
log_archive_dest_state_1='ENABLE'
log_archive_dest_state_2='ENABLE'
# define archive log naming format
log_archive_format=%t+%s+%r.arc |
| dg_prodb.ora |
remote_login_passwordfile='EXCLUSIVE'
# set max_processes equal to max_connections + 1 for local
log_archive_max_processes=4
log_archive_config='DG_CONFIG=(prodb,proda)'
db_unique_name='prodb'
# db_name='proda'
# service_names='proda'
fal_client=prodb
fal_server=proda
standby_file_management='auto'
log_file_name_convert=' ',' '
log_archive_dest_1= 'LOCATION=/app/oracle/product/fast_recovery_area/arch
valid_for=(all_logfiles,all_roles) db_unique_name=prodb'
log_archive_dest_2='service=dglogshipa valid_for=(online_logfile,primary_role) db_unique_name=proda
NET_TIMEOUT=15 REOPEN=60 OPTIONAL MAX_CONNECTIONS=3'
log_archive_dest_state_1='ENABLE'
log_archive_dest_state_2='ENABLE'
# define archive log naming format
log_archive_format=%t+%s+%r.arc |
| Prepare omega1 for backup |
SQL> startup mount;
SQL> show parameter %archive%
SQL> SELECT inst_id, log_mode FROM v$database;
SQL> alter database archivelog;
SQL> alter database force logging;
SQL> alter database add supplemental log data;
SQL> alter database open;
SQL> archive log list;
SQL> alter system switch logfile;
SQL> archive log list;
SQL> SELECT dest_id, valid_type, valid_role, valid_now
FROM gv$archive_dest; |
| Create RMAN catalog and backup omega1 |
-- as oracle on bigdog
$ sqlplus / as sysdba
-- using OMF
CREATE TABLESPACE cat_tbs;
CREATE USER repoomega#
IDENTIFIED BY repoomega#
DEFAULT TABLESPACE cat_tbs
TEMPORARY TABLESPACE temp
QUOTA UNLIMITED ON cat_tbs;
GRANT create session, recovery_catalog_owner TO repoomega#;
GRANT execute ON dbms_stats TO repoomega#; -- for class only |
| Duplicate database for Standby on omega2 |
SQL> conn / as sysdba
SQL> startup nomount;
$ rman target sys/oracle1@proda auxiliary /
RMAN> duplicate target database for standby nofilenamecheck;
RMAN> exit; |
| On both servers create a password file |
$ cd $ORACLE_HOME/dbs
$ ls -la
orapwd file=orapwprodb password=oracle1
set linesize 121
col name format a30
col value format a50
SELECT name, value
FROM gv$parameter
WHERE name LIKE '%remote_login%'; |
| Step 3: Configure Standby Redo Logs |
Minimally, the configuration should have
one more standby redo log file group than the number of online redo log
file groups on the primary database.
However, the recommended number of standby redo log file groups is
dependent on the number of threads on the primary database.
Use the following equation to determine an appropriate number of
standby redo log file groups:
(max. number of logfiles for each thread + 1) * max. number of threads
Using this equation reduces the likelihood that the primary
instance's log writer (LGWR) process will be blocked because a standby
redo log file cannot be allocated on the standby database.
For example, if the primary database has 2 log files for each
thread and 2 threads, then 6 standby redo log file groups are needed on
the standby database.
By default Oracle has 1 thread with three log files so: (3+1) * 1 = 4 |
| |
| Physical Standby Commands |
| Complete applying all available redo in preparation for a failover.
Use the FINISH clause only in the event of primary database failure. |
ALTER DATABASE ACTIVATE PHYSICAL STANDBY DATABASE [FINISH]; |
| ALTER DATABASE ACTIVATE PHYSICAL STANDBY DATABASE FINISH; |
| Create standby logfile |
ALTER DATABASE ADD STANDBY LOGFILE '<path_and_file_name>' SIZE <integer> <M | G>; |
| ALTER DATABASE ADD STANDBY LOGFILE '/app/oracle/product/dbs/stdbylog01a.log'
SIZE 50G; |
| Switchover of a primary database to standby |
ALTER DATABASE <PREPARE | COMMIT> TO SWITCHOVER TO PHYSICAL STANDBY [WITH SESSION SHUTDOWN]; |
SELECT switchover_status FROM v$database;
ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY WITH SESSION SHUTDOWN;
-- on the "new" primary if it the first time
ALTER SYSTEM SET DB_CREATE_FILE_DEST = '/u01/oradata/orabase';
ALTER TABLESPACE temp ADD TEMPFILE; |
| Convert a primary to a standby |
ALTER DATABASE CONVERT TO <PHYSICAL | SNAPSHOT> STANDBY; |
| ALTER DATABASE CONVERT TO PHYSICAL STANDBY; |
| Start redo apply as a foreground process |
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE; |
| ALTER DATABASE RECOVER MANAGED STANDBY DATABASE; |
| Stop redo apply |
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL; |
| ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL; |
| Start redo apply as a background process |
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT [FROM SESSION]; |
| ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT; |
| Cancel an apply time delay |
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE NODELAY; |
| ALTER DATABASE RECOVER MANAGED STANDBY DATABASE NODELAY; |
| Start real-time apply as a foreground process |
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE; |
| ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE; |
| Start real-time apply as a background process |
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE [DISCONNECT FROM SESSION]; |
| ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT FROM SESSION; |
| From the standby manually register log files from a failed primary |
ALTER DATABASE REGISTER [OR REPLACE] [PHYSICAL] LOGFILE <file_path_and_name>
[FOR <logminer_session_name>]; |
| ALTER DATABASE REGISTER LOGFILE '/u01/dest1/stdbylog01a.log'; |
| Change the protection mode |
ALTER DATABASE SET STANDBY DATABASE TO <AVAILABILITY | PERFORMANCE | PROCTECTION>; |
SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE PERFORMANCE;
ALTER DATABASE OPEN; |
| Switchover of a primary database to standby |
ALTER DATABASE <PREPARE | COMMIT> TO SWITCHOVER TO ....; |
SELECT switchover_status FROM V$database;
ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY WITH SESSION SHUTDOWN; |
| At failover send unsent redo to the standby |
ALTER SYSTEM FLUSH REDO SQL |
| ALTER SYSTEM FLUSH REDO SQL; |
| |
| Active Data Guard |
| Description |
Active Data Guard isn't a type of
standby. It is the option that allows you to open a physical standby
read only and restart the apply.
It also includes the right to turn on block change tracking. In
11.2 it also includes automatically repairing corrupt blocks. This
option requires that your purchase an additional license. |
| Steps to convert a physical standby into an Active Data Guard standby |
-- stop redo application
alter database recover managed standby database cancel;
-- if RAC shut down all but one instance
-- the database should now be mounted but not open. Open the database in read-only mode
alter database open read only;
-- restart managed recovery
alter database recover managed standby database using current logfile disconnect;
-- verify that a fast recovery area has been configured. |
| |
| Snapshot Standby |
| Description |
A snapshot standby database is a fully
updatable standby database that is created by converting a physical
standby database into a snapshot standby database.
A snapshot standby database receives and archives, but does not
apply, redo data from a primary database.
Redo data received from the primary database is applied when a
snapshot standby database is converted back into a physical standby
database, after discarding all local updates to the snapshot standby
database.
A snapshot standby database typically diverges from its primary
database over time because redo data from the primary database is not
applied as it is received.
Local updates to the snapshot standby database will cause
additional divergence.
The data in the primary database is fully protected however,
because a snapshot standby can be converted back into a physical standby
database at any time, and the redo data received from the primary will
then be applied.
A snapshot standby database provides disaster recovery and data
protection benefits that are similar to those of a physical standby
database.
Snapshot standby databases are best used in scenarios where the
benefit of having a temporary, updatable snapshot of the primary
database justifies increased time to recover from primary database
failures.
Snapshot standby does not require any extra licensing as it is part of Data Guard in the EE license. |
| Steps to convert a physical standby into a Snapshot standby |
-- on the physical standby stop the recovery process
alter database recover managed standby database cancel;
-- if RAC shut down all but one instance the database should now be mounted but not open. Open the database in read-only mode
alter database open read only;
-- restart managed recovery
alter database recover managed standby database disconnect;
-- verify that a fast recovery area has been configured
SQL> ALTER DATABASE CONVERT TO SNAPSHOT STANDBY; |
| Convert a snapshot to physical standby |
SQL> ALTER DATABASE CONVERT TO PHYSICAL STANDBY; |
| |
| Related SQL Statements |
| Examine Database Characteristics |
SELECT inst_id, open_resetlogs, open_mode, protection_mode, protection_level
FROM v$database;
SELECT inst_id, remote_archive, activation#, switchover#, database_role
FROM v$database;
SELECT inst_id, archivelog_compression, switchover_status, dataguard_broker, guard_status
FROM v$database;
SELECT inst_id, supplemental_log_data_min, supplemental_log_data_pk,
supplemental_log_data_ui, supplemental_log_data_fk,
supplemental_log_data_all, force_logging
FROM v$database;
col name format a20
col db_unique_name format a20
SELECT inst_id, current_scn, db_unique_name, name, standby_became_primary_scn
FROM v$database;
col fs_failover_observer_host format a20
SELECT fs_failover_status, fs_failover_current_target,
fs_failover_observer_present, fs_failover_observer_host
FROM v$database; |
| Data Guard Monitoring |
col hostname format a30
SELECT db_name, hostname, log_archived, log_applied, applied_time,
log_archived-log_applied AS GAP
FROM (
SELECT name AS DB_NAME
FROM v$database),
(
SELECT UPPER(SUBSTR(host_name, 1, (DECODE(INSTR(host_name,'.'), 0,
LENGTH(host_name), (INSTR(host_name,'.')-1))))) HOSTNAME
FROM v$instance),
(
SELECT MAX(sequence#) AS LOG_ARCHIVED
FROM v$archived_log
WHERE dest_id = 1
AND archived = 'YES'),
(
SELECT MAX(sequence#) AS LOG_APPLIED
FROM v$archived_log
WHERE dest_id = 2
AND applied = 'YES'),
(
SELECT TO_CHAR(MAX(completion_time),'DD-MON/HH24:MI') AS APPLIED_TIME
FROM v$archived_log
WHERE dest_id = 2
AND applied = 'YES'); |
| Switchover Demo |
SELECT name, current_scn, guard_status, switchover_status, database_role, checkpoint_change#, archive_change#,
archivelog_change#, db_unique_name, platform_name
FROM v$database;
ALTER SESSION SET NLS_DATE_FORMAT='DD-MON-YY HH24:MI:SS';
SELECT sequence#, first_change#, next_change#, standby_dest, completion_time, is_recovery_dest_file, fal
FROM v$archived_log;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT;
ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY WITH SESSION SHUTDOWN WAIT;
STARTUP;
ALTER SYSTEM SET JOB_QUEUE_PROCESSES=0;
ALTER SYSTEM SET AQ_TM_PROCESSES=0;
ALTER DATABASE COMMIT TO SWITCHOVER TO STANDBY WITH SESSION SHUTDOWN WAIT;
SELECT SWITCHOVER_STATUS FROM GV$DATABASE;
ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY WITH SESSION SHUTDOWN WAIT; |
| Diagnose Logical Data Guard Failures |
-- determine replication lag
SELECT name, value, unit
FROM v$dataguard_stats;
-- determine the schema was maintained by SQL Apply
SELECT owner
FROM dba_logstdby_skip
WHERE statement_opt = 'INTERNAL SCHEMA'
ORDER BY 1;
-- check the standby site for for error messages
col error format a30
col destination format a30
SELECT dest_id, status, destination, error
FROM v$archive_dest
ORDER BY 1; |
