ORACLE9I 1Z0-032认证知识点总结摘要（三）

The user only needs to remember one password, which opens the wallet to access his or her credentials, Wallet Manager is used to authenticate the user to multiple services.

 

The V$DATAFILE_HEADER dynamic performance view displays the error information related to data files when an internal read performed by Oracle fails. Apart from this, the view displays the status of the file and whether a file needs media recovery to be performed.

 

To obtain detailed information about the datafiles associated with the temporary tablespace, you must query the V$TEMPFILE or DBA_TEMP_FILES views in Oracle9i. Some of the important columns in the V$TEMPFILE dynamic performance view are NAME, FILE#, TS#, STATUS, ENABLED, AND BYTES.

 

The TNSPING utility enables you to check for connectivity of a database service without specifying any username and password.

 

Database supplemental logging allows you to specify logging of primary keys, unique indexes or both. With this enabled, whenever a DML is performed, the columns involved in the primary key or unique index are always logged even if they were not involved in the DML.

This only takes effect for statements which have not yet been parsed. It also invalidates all DML cursors in the cursor cache and therefore has an effect on performance until the cache is repopulated.

 

You can create an automatic space management segment only in a locally managed tablespace. The FREE_BLOCKS procedure refers to the blocks in a segment below the high water mark whose number of rows falls below the PCTUSED attribute, and therefore are candidate for new inserted rows. An automatic space management segment usage eliminates the need to specify the PCTUSED, FREELISTS, and FREELIST GROUPS parameters. So you CANNOT successfully invoke the DBMS_SPACE.FREE_BLOCKS procedure on an automatic space management segment.

 

The Log Writer updates the online redo logs with the transactions. It can also update the local archived redo logs and send online redo logs transactions to the standby databases. The archiver saves the online redo log transactions on either local or standby archive logs. The Fetch Archive Log(FAL) client gets redo log transactions from the primary database. When it detects an archive log gap on the standby database, it initiates a request to the FAL server to automatically send and archive the primary database’s redo log transactions. The FAL server exists on the primary database server, and it services requests from FAL clients.

 

Before the issuing the dbms_redefinition_start_redef table procedure call it’s recommended to invoke the dbms_redefinition.can_redef_table procedure and create an empty interim table with all the desired characteristics. Dbms_redefinition_start_redef procedure verifies that the table can be redefined online.

 

You can add or rename columns, change a heap table to an index-organized table and change the data type of a column from DATE to CHAR by using online redefinition of tables.

 

A workspace is a virtual database facility that enables you to maintain multiple versions of one row of data and it enables each workspace context to reference a different version of this row as compared to another workspace context, it’s possible to create workspace if there is no version-enabled table in the database.

 

To perform DML operations while using an Oracle Flashback image you can use a cursor. Oracle Flashback uses undo information to construct consistent data. The UNDO_RETENTION parameter must be set and the UNDO tablespace must be large enough so that undo generated during the period we want to query will not be overwritten.

 

Prior to Oracle9i, you could create bitmap indexes on a single table. Bitmap indexes are very useful in data warehousing environment for low-cardinality columns. Oracle9i extents this concept to a bitmap join index that optimizes the joining of two or more tables. A bitmap join index is a space- and performance-efficient technique. By predetermining associations, bitmap join indexes eliminate the large volumes of data generated with Cartesian products performed in a join operation.