分类： Oracle
2007-12-14 11:53:15
RMAN command CROSSCHECK enables you to crosscheck the availability of the backup sets by verifying the information stored in its repository with the backup sets that are physically available in the designated storage medium.
Direct load insert can be implemented either in the serial mode or the parallel DML mode. To load data in the serial mode, you must activate the direct load insert by specifying the APPEND hint either immediately after the INSERT statement or within the subquery. You can also use the APPEND hint with
Checkpoints, at the database or data file level, occur automatically when the database encounters the following conditions: when a log switch occurs, when configured through the database initialization parameter LOG_CHECKPOINT_INTERVAL and LOG_CHECKPOINT_TIMEOUT
,when an online database backup begins, when a tablespace is taken offline
You must use the cancel-based recovery to perform an incomplete media recovery if a current redo log is damaged and is not available to perform recovery. Another reason for using cancel-based recovery is when an archived redo log file needed for recovery is unavailable either due to the loss of the file or corruption. Archiving to multiple destinations or backing up the files more frequently can avoid such errors.
The SET command enables you to dynamically set the values for the listener parameters. The values persist till the listener is stopped.
The initialization parameter FAST_START_MTTR_TARGET enables you to specify the amount of time(in seconds) the database should take to perform crash recovery of a single instance. This value is internally converted to a set of parameters that modify the operation of Oracle in such a way that recovery time is as close to this estimate as possible.The initialization parameter FAST_START_IO_TARGET specifies the number of I/Os that should be needed during creash or instance recovery. This parameter has been deprecated in favor FAST_START_MTTR_TARGET parameter. You must disable the initialization parameters FAST_START_IO_TARGET, LOG_CHECKPOINT_INTERVAL, and LOG_CHECKPOINT_TIMEOUT parameters when using FAST_START_MTTR_TARGET. Setting these parameters to active values obstructs the normal functioning of FAST_START_MTTR_TARGET, thereby resulting in unpredictable results.
A process failure is due to the abnormal termination of a process. Oracle handles these types of failures by using a background process called PMON. PMON identifies the terminated session and resets the status of the active transaction table, releases locks, and removes the process ID rom the list of active processes.
The multithreaded Heterogeneous Service (HS) Agents architecture has three kinds of threads:
A single monitor thread, several dispatcher threads and several task threads.
Prior to Oracle9i, DDL statements were recorded as a set of DML statements on internal tables. It was no simple task to review these DML statements and realize that a DDL operation has been performed. You could almost forget this when trying to determine the actual DDL statement that sourced these DML statements. Oracle9i records the original DDL statement in the redo logs, and LogMiner lists this DDL statement followed by the set of generated DML statements. When you query V$LOGMNR_CONTENTS, you can see DDL under the OPERATION column, and the DDL statement itself under the SQL_REDO column.
You can make a shared server-side initialization parameter file available to all instances of a Real Application Clusters database by including an SPFILE parameter in each instance-specific initialization file. You still have to store a copy of the initialization parameter file on each node to facilitate startup of the instances. You can avoid distributing copies by converting this initialization parameter file into a Spfile. Then you put the one parameter as shown here, in the initialization parameter file for each instance:
Spfile=oracle/home:/config/spfile
Trial Recovery allows the Administrator to determine how many blocks are affected by corruption, mark then as sorrupt in memory to allow the TEST recovery proceed to completion. By default, trial recovery always attempts to corrupt blocks in memory if this action allows trial recovery to proceed. In other words, trail recovery by default can corrupt an unlimited number of data blocks. You can specify the allow n corruption clause on the RECOVER TEST statement to limit the number of data blocks trial recovery can corrupt in memory. It can be invoked by adding the TEST option to any RECOVER command.
When a client machine initiates a shared server connection to the database in Oracle9i, the listener uses the direct handoff whenever possible. This connection process requires fewer network calls and , accordingly, less overhead.
When the listener receives the request from the client for a shared server connection, it locates the address of the least loaded dispatcher process. In previous versions, the next step would have been to pass this address back to the client for the client to contact the dispatcher again over the network. Instead, in Oracle9i’s direct handoff method, the listener hands the connection request to the dispatcher, the dispatcher communicates directly with the client to establish a connection without the need for the additional network calls that were required in previous versions.
It is not possible to export rows with collection data types. The export client, exp, may do some charset conversions while writing data to the dump file. The direct path export type is not noted in the output to the screen ,in the export log file, and the export dump file. The direct path export uses only the buffer cache and writes directly to the export file on the disk. You need to use the parameter DIRECT=Y to do a direct path export.
