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发布时间:2009-04-28 11:24:05

在审计对象权限时可以通过not existes选项可以对不存在的对象以及语句进行审计。[@more@]SQL> show userUSER 为 "XYSWCH"SQL> audit not exists;审计已成功。SQL> select * from tt7;select * from tt7 *第 1 行出现错误:ORA-00942: 表或视图不存在SQL> select action_name,obj_name from dba_audit_exists where obj_name='TT7';ACTION_NAME OBJ_NAME---------------------------- ----------SELECT TT7SQL>--审计结构会记录在视图dba_audit_exists中......【阅读全文】

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发布时间:2009-04-28 10:14:53

在使用对象权限审计时如果使用on default选项,有一下几个方面需要注意:1、设置on default之后,它仅对之后创建的对象生效2、on default对之后创建的对象永远生效,即使以后设置了noaudit all(或者其他)on default;除非单独对某个对象设置noaudit all(或者其他)on object_name才能彻底取消on default选项引起的审计3、使用view时,对表和view同时记录审计结果(union)[@more@]ON DEFAULT Specify ON DEFAULT to establish the specified object options as default object options for subsequently created objects. After you hav......【阅读全文】

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发布时间:2009-04-26 00:24:22

n年前测试成功过,最近至少1年一直都无法成功,尤其是讲课时成功不了很痛苦,今天把各种情况组合了一下,最后得出成功的配置步骤。[@more@]SQL> SHOW PARAMETER OSNAME TYPE VALUE------------------------------------ ----------- ------------------------------optimizer_index_cost_adj integer 100os_authent_prefix stringos_roles boolean FALSEremote_os_authent boolean FALSEremote_os_roles boolean FALSEtimed_os_statistics integer 0--注意一定要把os_authent_prefix的default值OPS$改成null(去掉)SQL> host hostnam......【阅读全文】

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发布时间:2009-04-24 19:16:44

ash and awr[@more@]The ASH contains recent information on active sessions sampled every second. The AWR takes snapshots of the database every hour, so the information in the AWR could be almost an hour old and will not help in diagnosing issues that are current on the database. Typically, to resolve issues currently on the database, detailed information pertaining to the last 5 or 10 minutes is critical. Because recording session activity is expensive, ASH samples V$SESSION every second and reco......【阅读全文】

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发布时间:2009-04-24 18:56:44

Temporary Tablespace Group[@more@]A temporary tablespace group can be thought of as a shortcut for a list of temporary tablespaces.A temporary tablespace group consists of only temporary tablespaces.A temporary tablespace group has the following properties:It contains at least one temporary tablespace. There is no explicit limit on how many tablespaces are contained in a group.It has the same namespace as tablespaces. It is not possible for a tablespace and a temporary tablespace group to have t......【阅读全文】

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发布时间:2009-04-24 18:42:39

Base Statistics and Metrics[@more@]Base statistics represent the raw data collected. For example, counting the number of physical reads in the system since startup is a base statistic.Metrics are secondary statistics derived from base statistics. Most metrics track the rates of change of activities in the Oracle database.For example, the average physical reads in the system in the last 60 minutes is a metric. Metrics are used by internal client components forsystem health monitoring, problem det......【阅读全文】

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发布时间:2009-04-24 18:39:24

AWR(Automatic Workload Repository)[@more@]This component is the central element of the new manageability infrastructure. It provides services to internal Oracle server components to collect, process, maintain, and access performance statistics for problem detection and self-tuning purposes.AWR is the infrastructure that provides services to Oracle Database 10g components to collect,maintain, and utilize statistics for problem detection and self-tuning purposes.The AWR infrastructure consists of ......【阅读全文】

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发布时间:2009-04-19 08:59:16

有关一致性读的过程确实非常复杂...希望有一天能以试验的方式清晰的解读这个过程...[@more@]CREATING A READ CONSISTENT VIEW STEPS 1. Read the Data Block. If the block is resident in memory, create a clone to perform the undo. 2. Read the Row Header. 3. Check the LockByte to determine if there is an ITL entry. 4. Read the ITL to determine the Transaction ID.Automatic UNDO Internals5. Read the Transaction Table. If the transaction has been committed and has a System Commit Number less than the query’s ......【阅读全文】

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发布时间:2009-04-19 08:32:51

doc解释的很清楚,看doc吧The number of undo segments created and brought online is a function of the SESSIONS parameter. The algorithm is roughly 1 undo segment for each 5 sessions. All undo segments are placed online when the sessions parameter is set to 46 or greater. The lower limit was not tested, as the minimum value for the sessions parameter in the test database was 16, which was derived from the minimum number of processes (10) for the database. These are sized according to the autoalloca......【阅读全文】

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发布时间:2009-04-19 08:10:58

当并发事务的数量超过在线undo segment的数量时undo segment被smon自动创建, 我记得不知道在哪儿看到过说:undo segment的创建会记录在alert中,但是没有发现...还是记错了...One of the benefits of AUM is the dynamic creation of undo segments as needed. When the number of concurrent transactions exceeds the number of online undo segments, more segments are brought online. If there are offline segments in the current undo tablespace, they are the first ones to be used. If no offline segments exist, new ones......【阅读全文】

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发布时间:2009-04-19 07:59:09

When a transaction needs more space in an undo segment, there is a fixed algorithm the determines when extents are reused.. The transaction will first attempt to reclaim expired extents from the current segment, then expired extents from another segment. The third method will be to autoextend the datafile(s), if this is set. Next, the unexpired extents from the current segment and other segments will be allocated, as long as the extents do not contain uncommitted transactions. Finally, an error ......【阅读全文】

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发布时间:2009-04-19 07:30:00

什么是BLOCK CLEANOUT![@more@]BLOCK CLEANOUT When a data block is altered, important transaction information is written to the block along with the data changes. When the transaction is committed, the block is not rewritten to reflect the new transaction state. The next transaction, whether a SELECT or INSERT/UPDATE/DELETE, will ‘discover’ the out of date information and update the block to reflect the committed state of the previous transaction. This is called ‘delayed block cleanout.’ It i......【阅读全文】

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发布时间:2009-04-13 13:04:24

Dump undo blocks associated with specific transaction Alter system dump undo block ‘segment_name’ xid usn slot seq; [@more@]SQL> insert into t select object_id,object_name from dba_objects;已创建11354行。SQL> select xidusn,xidslot,xidsqn,xid from v$transaction; XIDUSN XIDSLOT XIDSQN XID---------- ---------- ---------- ---------------- 2 15 212 02000F00D4000000SQL> select ubafil,ubasqn,ubarec,start_ubafil,start_ubasqn,start_ubarec from v$transaction; ......【阅读全文】

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发布时间:2009-04-07 11:08:51

留下了很多疑问,暂时记录一下slot被覆盖之前会被保存下来吗?这个我想肯定不会.........如果是这样,为什么在覆盖之后没有出现ora-01555?[@more@]rollback segment rbs2中一共有21个slot,连续启动20个事务占去20个slot,目的只是为了测试的需要,只留一个slot不停的操作事务,目的是能让其他事务覆盖slot从而测试consistentread的过程和ora-01555:20个事务启动之后的slot使用如下:session 2:SQL> select xidslot,start_time from v$transaction order by xidslot;XIDSLOT START_TIME------- -------------------- 0 04/07/09 0......【阅读全文】

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发布时间:2009-04-05 22:36:56

slot被覆盖之后,delay block cleanout是的commit scn从undo header中的control scn获得。[@more@]SQL> select count(*) from tt1; COUNT(*)---------- 0SQL> select count(*) from tt2; COUNT(*)---------- 182224SQL> select distinct sid from v$mystat; SID---------- 159SQL> insert into tt1 select *from tt2;已创建182224行。SQL> show parameter db_cacheNAME TYPE VALUE------------------------------------ ----------- -------------------......【阅读全文】

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发布时间:2009-04-05 18:11:43

这是一个delay block cleanout的最基本的测试,slot被覆盖的情况再讨论。[@more@]session 1:SQL> insert into tt select * from tt;已创建180096行。SQL> select xidusn from v$transaction; XIDUSN---------- 37SQL> select usn,name from v$rollname where usn=37; USN NAME---------- ------------------------------ 37 _SYSSMU37$session 2--analyze table是ddl命令,在session 1中执行此命令会commit事务SQL> analyze table tt compute statistics;表已分析。--验证一下事务还在SQL> select ......【阅读全文】

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发布时间:2009-04-05 11:12:54

值得仔细研究[@more@]Undo/rollbackOverview Undo/rollback segment is used for transaction rollback and read consistent or flashback query. There’re two management methods: auto and manual, respectively called undo and rollback. The basic structure is the same. Every database should have two type undo/rollback space: system and user data. The system undo/rollback is allocated from system tablespace, it mainly used for dictionary data. In RAC/OPS environment, every instance has its own private undo......【阅读全文】

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发布时间:2009-04-04 23:44:10

貌似测的还不够精准,同时没有找到具体介绍10%的相应doc,暂时记录一下。[@more@]SQL> alter system set sga_target=0;系统已更改。SQL> show parameter db_cacheNAME TYPE VALUE------------------------------------ ----------- ------------------------------db_cache_advice string ONdb_cache_size big integer 88MSQL> alter system set db_cache_size=80m;系统已更改。SQL> create table tt tablespace users as select * from dba_objects;表已创建。SQL> insert into tt select *from tt;已创建11389行。SQL>......【阅读全文】

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