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High Availability | Oracle DBA – Tips and Techniques | Page 3
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Flashback query

  • Posted by Arjun Raja
  • On June 29, 2009
  • 0 Comments
FLASHBACK QUERY FLASHBACK QUERY feature allows you to perform queries on the database as of a certain time or user-specified SCN. FLASHBACK VERSIONS QUERY feature allows you to use the VERSIONS clause to retrieve all of the versions of the rows that exist between two points in time, or two SCN’s. YOU REQUIRE THE SELECT […]
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Flashback table

  • Posted by Arjun Raja
  • On June 29, 2009
  • 0 Comments
FLASHBACK TABLE Only FLASHBACK DATABASE requires flashback to be ‘ON’ since only FLASHBACK DATABASE uses flashback logs in the flash_recovery_area. All other forms of FLASHBACK use the recycle bin and undo_tablespace. Important info: You cannot ‘flashback table to before drop’ a table which has been created in the SYSTEM tablespace. The table is sent to […]
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FLASHBACK DATABASE

  • Posted by Arjun Raja
  • On June 29, 2009
  • 0 Comments
FLASHBACK DATABASE Flashback database allows you to rollback database to a time in the past. Useful if you have : 1. Dropped user 2. Truncated table 3. Batch job:Partial changes. PRE-REQUISITE: DATABASE MUST BE IN ARCHIVELOG MODE AND YOU MUST SET FLASHBACK ON( BY DEFAULT IT IS OFF) FLASHBACK LOGS ARE CREATED IN YOUR FLASH_RECOVERY_AREA […]
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ARCHIVE AREA FULL – CONNECT INTERNAL UNTIL FREED

  • Posted by Arjun Raja
  • On June 29, 2009
  • 0 Comments
When a database is running in ARCHIVELOG mode, if the area which stores the archivelogs on disk gets full, the database comes to a halt and can be accessed only as a sysdba. The error message when you try to connect as a normal user is ‘ CONNECT INTERNAL UNTIL FREED’ If the following parameter […]
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10g Data Guard Broker Fast Start Failover

  • Posted by Gavin Soorma
  • On June 25, 2009
  • 0 Comments
FAST START FAILOVER IS DISABLED BY DEFAULT Configuration Name: streams2.hq.emirates.com Enabled: YES Protection Mode: MaxAvailability Fast-Start Failover: DISABLED Databases: streams2 - Primary database blade08 - Physical standby database Current status for "streams2.hq.emirates.com": SUCCESS PREPARE TO ENABLE TO FAST START FAILOVER DGMGRL> EDIT DATABASE 'streams2' SET PROPERTY FastStartFailoverTarget = 'blade08'; Property "faststartfailovertarget" updated DGMGRL> EDIT DATABASE […]
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Using FLASHBACK to Reinstate a Standby after a FAILOVER

  • Posted by Gavin Soorma
  • On June 25, 2009
  • 0 Comments
PERFORM A FAILOVER USING DATA GUARD BROKER DGMGRL> failover to 'standby_blade07'; Performing failover NOW, please wait... Failover succeeded, new primary is "standby_blade07" On the NEW PRIMARY issue this command to obtain the SCN to FLASHBACK the old primary(new standby) to SQL> conn / as sysdba Connected. SQL> SELECT TO_CHAR(STANDBY_BECAME_PRIMARY_SCN) FROM V$DATABASE; TO_CHAR(STANDBY_BECAME_PRIMARY_SCN) ---------------------------------------- 2147132 FLASHBACK […]
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Some top causes for unplanned outages

  • Posted by Gavin Soorma
  • On June 23, 2009
  • 1 Comments
I have quickly thought about some of the events which had caused unplanned downtime at my past organisation. Idea is to share the same and ensure our current monitoring infrastructure is taking into account aspects discussed below – better to learn from other’s experiences than to experience it yourself.   Listener log file grew > […]
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Some FLASHBACK DATABASE examples using RMAN and SQL*PLUS

  • Posted by Gavin Soorma
  • On June 18, 2009
  • 1 Comments
Wrong Update SQL> update customers set credit_limit=100000;  Shutdown the database  Startup mount the database  invoke rman  $ rman target /  Flashback database to time one hour prior to current time  RMAN>  FLASHBACK DATABASE TO TIME ‘(SYSDATE-1/24)’;  Starting flashback at 27-JUN-05 using target database controlfile instead of recovery catalog allocated channel: ORA_DISK_1 channel ORA_DISK_1: sid=156 devtype=DISK […]
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Flashback Database – Normal and Guaranteed Restore Points

  • Posted by Gavin Soorma
  • On June 18, 2009
  • 1 Comments
  Normal Restore Points  If the db_recovery_dest_file_size has been allocated less space then what is required for the flashback transaction logs as dictated by the db_flashback_retention_target parameter, then the flashback logs are deleted to free up space for the additional logs that are being generated. Alert log will show also that flashback logs are being […]
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