Velpuri, Anand Adkoli. Click here if your download doesn"t start automatically Oracle8i Backup & Recovery (Oracle Press) Rama Velpuri, Anand Adkoli. Includes information that Velpuri, Anand Adkoli for online ebook. Oracle8i Backup. ORACLG«Oracle Press Oracle Backup & Recovery Rama Velpuri Osborne McGraw-Hill Berkeley New York St. Louis San Francisco Auckland Bogota Hamburg. Oracle8i Backup & Recovery by Rama Velpuri. Read online, or download in secure PDF format. Oracle8i Backup & Recovery Includes information that every Oracle administrator and programmer must know to maximize uptime and.
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RMAN will give you enhanced recovery capabilities like block level recovery. Data Guard gives you disaster recovery, failover site capabilities. If the confines of things that cannot be changed includes noarchivelog mode, then you have resigned yourself to losing all data created during some period of time the time between backups.
You have resigned yourself to suffering downtime regularly have to shutdown to backup in noarch mode. I don't know what are the confines, so really cannot say. If you value your data, your work -- you will get into archivelog mode ASAP thanks Tom, May 04, - pm UTC Reviewer: A reader perhaps it was a bit presumptuous to declare that "things cannot be changed" As you explained a day's worth of work can cost a lot..
Currently I am using sqlbacktrack to do the hot backup.
To my surprise, I was able to do table level recovery using sqlbacktrack. It used the method of restoring the required tablespace where table resided and system,rbs tablespace and used the create controlfile to create the aux database and then retrived the table from the aux database. And it was all menu driven. I was wondering, if the same functionality exists in RMAN as well. Sqlbacktrack was able to provide me full table create statement and all data insert statements.
With RMAN online backups, a different mechanism ensures block consistency. Thus you do not place tablespaces into any special mode for backup. There are usually two steps to a perform a media recovery: The optional first step is restore, which is a simple copying of files from the backup system to the database locations.
The second step is the recover step, when the server applies the archive and online redo logs. Normally when people refer to recovery, they are referring to the restore phase. Read-Only Tablespaces The intention is to avoid taking repeated backups of data that does not change, and not to protect table row data against alteration.
Note: Tables in a read-only tablespace can be dropped. Even if you do not change any data, the data files are written to during every database open, close, and checkpoint, if the database is in normal mode. The data files of a tablespace set into read-only mode will not be written to, and are allowed to be out of date compared to the other data files.
You do not perform media recovery on a readonly tablespaces data files, you only restore them.
Offline Tablespaces There may be reasons for only having a partial set of the database available. Offlining a tablespace causes the server to close the data files, thus freeing them for some operation for example, moving to shelf storage.
At some later time, the data files are returned to their original location and can be made online again. This occurs regardless of whether or not data was in the cache. Note that if you offline files, as opposed to offline tablespaces, you do not get a choice. The process is immediate, thus requiring recovery when placing the tablespace online again. Constraint inconsistency Logical inconsistency Structural inconsistency Physical inconsistency At the block level At the inter-block level When is the Database Inconsistent?
The term inconsistent is often used, but can have several levels of meaning.
If the data schema presumes a constraint for example, a foreign key constraint then if there is data in the database that violates that, then we have a constraint inconsistency.
This will not occur in normal operation if database constraints are used. If this happens, when no constraints are used, only implied, then this is called a logical inconsistency. It might happen if an older version of a table that participates in a relation with other tables is imported. From the database point of view, the data is correct, there are no corruptions, but from the application point of view the database is inconsistent.
If the database does not contain the files the dictionary says it should, then there is a gross structural inconsistency. Normally the database will refuse to start until the fault is remedied. Another form for structural inconsistency is if the index entries do not point to the correct row.
This is a bug if it happens with the exception for secondary indexes on IOTs. Terminology and Architecture Chapter 1 - Page 19 Inside each block there are many structures, apart from the row data of a table. There are a number of pointers between these structures. If these pointers are incorrect, this can be described as physical inconsistency. Some pointers refer to another block akin to foreign keys. If they point to the wrong block, or if the other block does not have the content it should have ITL pointers to Undo entries, for example, as explained in DSI Space and Transaction Management , then there is physical inconsistency between blocks.
Many of the algorithms implemented for processing capabilities mean that at any stage during normal database operation, different portions of the database and the memory structures used to access it are inconsistent with regard to one another.
Consider that the database is the physical files in which we store data, and the instance is the memory structures. We know that database blocks are read from the disk into memory buffers and are then modified while resident in these buffers. Many changes can occur before the blocks are written back into the data files by the LRU algorithm.
These blocks are therefore from a later state in time than blocks on disk, and perhaps than other blocks in memory. The database is therefore inconsistent, and anything other than a controlled graceful shutdown will leave the database inconsistent. Another way of defining physical inconsistency is the following: if not all the blocks in a data file or database are from the same point in time that is, assuming all blocks have been flushed from the cache , then the data file or database, respectively, is physically inconsistent.
Atomicity: A transactions changes to the state are atomic: either all happen or none happen. These changes include database changes and messages.
Example: A mail note is only sent after one commits. When it is sent, the entire mail note is sent. Consistency: A transaction changes the state of the database from one coherent state to a new coherent state.
The actions taken as a group do not violate any of the integrity constraints associated with the state. This requires that the transaction be a correct program.
The view of an object does not change within the transaction. Example: While you are reading a mail message, the content will not change; the same version of the mail will remain a constant whether or not there are other concurrent modifications. Isolation: Even though transactions execute concurrently, it appears to each transaction, T, that others executed either before T or after T, but not both.
T appears to be the only user on the system even though it is executing with other concurrent transactions.
Other uncommitted changes or committed changes after a certain timestamp are ignored within your own transaction. Example: While writing or sending e-mail, other people can be doing the same thing. Subsequently, there will be an order or sequence of mail notes. Terminology and Architecture Chapter 1 - Page 21 The Isolation functionality is handled by read-consistent blocks, which use the undo data.
Durability: After a transaction completes successfully commits , its changes to the database state survive failures. Example: If the mail system fails, all sent mail is still in your inbox when you open your mailbox again. The Oracle server architecture needs to enforce these transactional properties while at the same time allowing for concurrent processing, processing speed, and so forth.
Database blocks are read from the disk into memory buffers within the SGA. These blocks are then modified while resident in these buffers, with least recently used LRU algorithms and other algorithms, meaning that many changes could take place before these blocks are written back into the data files.
The problem that the Recovery module must address is that of transactional durability. Terminology and Architecture Chapter 1 - Page 22 Durability Durability Transaction durability: After a transaction commits, it must survive failures.
Durability After a transaction completes successfully for example, commits , any changes that are made to the database state within the scope of this transaction must survive failures. A valid backup and recovery strategy enables the database to be restored to a consistent state in almost all scenarios.
Where this system fails is dependent on the planning and implementation by the database administrator, and the value that is placed on the data to be protected. If some loss can be tolerated, then a cheaper, more simplistic solution can be provided. However as the data value increases, more expensive and possibly more complex solutions may be devised, in an effort to protect against all possible failure scenarios.
The Oracle backup and recovery process is designed to accommodate both planned and unplanned outages, provided that sufficient resources are available. Typically it is considered a means of restoring consistency after an unplanned outage. Terminology and Architecture Chapter 1 - Page 23 Redo Versus Undo Redo Versus Undo Redo - After Image: Used to repeat a data modification, when the result has been lost Undo or Rollback - Before Image: Used to get the original data back after a change has overwritten it Redo and undo are handled and stored separately in the Oracle server architecture, but they are created simultaneously by any data change It is imperative for understanding the recovery architecture to distinguish between undo and redo.
In the Oracle server, the primary use of undo is to ensure isolation, and the primary use of redo is to ensure durability. A common misconception is that online redo log switches or reuse must not occur inside a transaction. A transaction that modifies a large amount of data may cause the redo log files to be filled up and overwritten several times, but that will not prevent the server from performing a rollback if requested or required, as rollback information is stored in the undo segment. Redo is stored in separate files in Oracle, the online redo log files, while undo is stored inside normal data files in the special undo tablespace or the special rollback segments.
Only undo is directly associated to a transaction, while redo is only implicitly associated to a transaction. Some redo is not part of the transaction with which it appears to be associated, for example delayed block cleanout changes.
Undo can be discarded after the transaction commits; redo can be discarded after the buffer cache is flushed or checkpointed. The words rollback and undo are synonyms. There are other ways the problem of before and after image journaling can be handled.
Some database manufactures have redo and undo in the same data structure, while others avoid the problem by disallowing concurrent readers and writers of table row data. Recall that the datafile header is a special datablock, and that the control file, too, is read and written in blocks but not cached data blocks like the data files.
Note that as a transaction generates redo it also generates undo, which in turn generates more redo. In practice, this is done backward: the server code first generates all the redo, then the undo, and lastly the data change. Bulk operations include direct inserts, create operations, and parallel operations.
For LOB segments not inline row data the redo can be suppressed separately from the table.