How to view the database in oracle

OracleResourceManager achieves resource optimization by dividing user groups, limiting concurrency and resource consumption, dynamic switching strategies, and monitoring and adjustment. 1. It groups users (such as REPORTING_GROUP, DEVELOPER_GROUP), allocates CPU resources according to priority, ensuring that critical tasks obtain higher quotas; 2. Controls the number of concurrent sessions, execution time and I/O upper limit to prevent system overload; 3. Automatically switch resource plans according to time periods, such as focusing on OLTP during the day and batch processing at night; 4. Provides views such as V$RSRC_CONSUMER_GROUP to monitor usage, and it is recommended to regularly check and adjust strategies to improve performance.

Oraclesequences and identitycolumns can generate self-value-added, but the mechanism is different from the applicable scenarios. 1. Oracle sequences are independent objects that can be used across tables, providing higher control flexibility, such as cache, looping, etc.; 2. The Identity column embeds the self-increment logic in the table column, simplifying the settings, suitable for simple scenarios and closer to MySQL/PostgreSQL usage; 3. The key differences are the scope of action (sequences are available globally, identity columns are limited to single tables), control ability (sequence functions are stronger) and ease of use (identity columns are more intuitive); 4. It is recommended to use identity columns in simple scenarios, and when complex systems or shared counters are required, the sequence is preferred.

Oracle uses undotablespace to store data images before transaction modification to support transaction consistency, rollback operations, and database-level read consistency. Its core functions include: 1. Rolling back uncommitted transactions; 2. Provide a consistent data read view; 3. Support recovery after instance or media failure; 4. Ensure ACID transaction properties. Oracle automatically manages the revocation segment and configures retention time through UNDO_RETENTION, while recycling the revocation data of the committed transaction when there is insufficient space. Common problems include ORA-01555 errors, high undo generation rates, and too small undo tablespaces. Therefore, the undo tablespace size should be set reasonably based on the workload. establish

Oracle instances should prioritize elegant shutdown using SHUTDOWNIMMEDIATE, and use SHUTDOWNABORT only when the database is unresponsive. 1.SHUTDOWNIMMEDIATE will block new connections, roll back active transactions, disconnect all sessions, and close database files normally to ensure data consistency; 2.SHUTDOWNABORT will directly terminate the instance, and will not roll back transactions or write to disk, resulting in instance recovery required for next startup; 3. Key differences include transaction rollback behavior, data integrity guarantee and startup impact; 4. Best practice is always the first choice to close immediately unless the database is completely stuck or is in a non-critical test environment.

OracleAdvancedQueuing(AQ)enablesasynchronousmessage-basedcommunicationwithinOracleDatabasethroughbuilt-inqueues.1.SetupqueuetablesanddefinemessagetypesusingDBMS_AQADMprocedurestocreatestructuredqueues.2.EnqueuemessageswithDBMS_AQ.ENQUEUE,optionallysp

Thealert.logfileinanOracledatabaseisacriticaltoolfortroubleshootingandmonitoring,recordingmajoreventsanderrorssuchasinstancestartup/shutdown,logswitches,tablespacechanges,internalerrors,recoveryprocesses,andjobfailures;itislocatedbydefaultunderthedia

ExternaltablesinOracleallowyoutoqueryexternalflatfilesasiftheywereregulardatabasetables.1.Theydonotstoredatainternallybutreferenceexternalfilesviametadata.2.YoucreatethemusingCREATETABLE...ORGANIZATIONEXTERNALwithspecificationsforfileformat,location,

InOracle,sharedlocksallowmultipleuserstoreaddatasimultaneouslybutblockmodifications,whileexclusivelocksgrantasingletransactionfullcontrol,blockingbothreadsandwrites.1.Sharedlocksareusedforreadingdatawithoutchangingit,enablingconcurrentreadsbutprevent