oracle备份数据库表分析数据库运维服务CitusDB：提供弹性计算能力(数据库运维开发)企业数据库市场很庞大，在这个领域既有Oracle这样行家，也有IBM(DB2)和微软(SQL Server)这样的跨界巨头
? 对于 SQL Server：? 以下为引用的内容：create view v_lhsy_user as select * from link_northsnow.lhsy.dbo.sys_user select * from v_lhsy_user 其中 lhsy 为远程的数据库名? sys_user 为表名? 对于 Oracle：? 以下为引用的内容：create view vvv as select * from link_ora..NORTHSNOW.SYS_USER select * from vvv; 其中 northsnow 为远程 Oracle 数据库服务器的一个用户名，SYS_USER 为该用户在该服务器上的一个表，要非常注意的是：数据库链接(link_ora)后面有两个点(..)，再往后面必须全部大写，查询的对象一般为表格或者视图，不能查询同义词
虽然这种蠕虫不会影响到数据库的运行，但是确实证明了在不加保护的Oracle数据库中这种情况是可能发生的
比如：在金融业务领域，有一个反洗钱的交易，从A到B，B到C，C到E，E到D和F，D又到B
如图4所示
UTL_HTTP的使用可能只是一个简单的单行调用，否则可以通过多个调用来处理诸如认证、代理以及cookies这一类的复杂过程
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亮点二：行业解决方案+组合产品推荐直接get据了解，华为云数据库结合多年行业经验及数据库云化改造技术，大幅优化传统数据库，拥有RDS for MySQL、GaussDB(for MySQL）、文档数据库服务DDS、GaussDB(for Redis）等多款产品
一个以 IPv6 格式给出的记录将只匹配 IPv6 连接，即使对应的地址在 IPv4-in-IPv6 范围内
注意：查询优化器只有在表统计信息保持最新的情况下使用 R-Tree 索引
WBML也支持对ODBC数据源的直接SQL查询
用户可以将自己添加到系统服务，使用一个内置的工作流系统开始一个批准过程
This is thearea that is the space allocated in main memory for each process to perform sorts. If the sort cannot be performed inmemory， temporary segments are allocated on disk to hold intermediate runs. Increasing the value of sort_area_sizewill reduce the total number of disk sorts， thus reducing disk I/O. This can cause swapping， if to little memory is leftover for other processes. Statements that will generate Temporary Segments include： Create Index， Select …… OrderBy， Distinct， Group By， Union， Unindexed Joins， Some Correlated Subqueries. Since temporary segments are created tohandle sorts that cannot be handled in memory， the initial extent default for temporary segments should be at least as large as the value ofsort_area_size. This will minimize extension of the segment.Deploying， Managing， and Administering the Oracle Internet PlatformPaper #224/ Page 5GOAL#2： GET DATA “CACHED” INTO MEMORYOnce you have enough memory allocated to Oracle， the focus must shift to ensuring that the most importantinformation is getting into memory and staying there. We will look at using x$bh and using the ‘cache’ parameter of‘alter table……’ to investigate this area below：A. TO SEE HOW FAST THE SGA GETS USING X$BHselect state， count（*）from x$bhgroup by state；STATE COUNT（*）--------- -----------------0 3711 429In the above result：Total DB_BLOCK_BUFFERS = 800Total that have been used = 429Total that have NOT been used = 371A BETTER QUERY：select decode（state，0， ''FREE''， 1， decode（lrba_seq，0，''AVAILABLE''，''BEING USED''），3， ''BEING USED''， state） "BLOCK STATUS"， count（*）from x$bhgroup by decode（state，0，''FREE''，1，decode（lrba_seq，0，''AVAILABLE''，''BEING USED''），3， ''BEING USED''， state）；BLOCK STATUS COUNT（*）AVAILABLE 779BEING USED 154FREE 167You can also view the init.ora parameters in the Performance Manager inside Oracle‘s Enterprise Manager as shownbelow：B. USING THE ‘CACHE’ PARAMETER OF ‘ALTER TABLE……’）If you find that “key” tables are being pushed out of memory， you may need to “pin” them into memory using theCACHE parameter. When you use this parameter， full table scans result in being placed on the “Most recently used”list instead of the “Least recently used” list. This keeps them in memory for future use. The following examplesinvestigate the syntax and uses of this command：EXAMPLE 1 （CREATE A TABLE WITH CACHE）CREATE TABLE TEST_TAB （COL1 NUMBER）TABLESPACE USERSCACHE；Deploying， Managing， and Administering the Oracle Internet PlatformPaper #224/ Page 6NOCACHE is the Default！EXAMPLE 2 （ALTER A TABLE TO CACHE）ALTER TABLE TEST_TABCACHE；EXAMPLE 3 （THE CACHE HINT）SELECT /*+ CACHE（CUST） */ ENAME， JOBFROM CUSTWHERE TABLE_NAME = ''EMP''；EXAMPLE 4 （THE NOCACHE HINT）SELECT /*+ FULL（CUST） NOCACHE（CUST） */ ENAME， JOBFROM CUSTWHERE TABLE_NAME = ''EMP''；GOAL#3： FIND PROBLEM QUERIES “HURTING” MEMORYA single index or a single query can bring an entire system to a near standstill. By using v$sqlarea， you can find theproblem queries on your system. Below， the example shows how to find the problem queries. I am searching forqueries where the disk reads are greater than 10，000. If your system is much larger， you may need to set this to ahigher number.EXAMPLE 5 （FINDING THE LARGEST AMOUNT OF PHYSICAL READS BY QUERY）select disk_reads， sql_textfrom v$sqlareawhere disk_reads > 10000order by disk_reads desc；DISK_READS SQL_TEXT------------------ -----------------------------------------------------------------12987 select order#，columns，types from orderswhere substr（orderid，1，2）=：111131 select custid， city from customerwhere city = ‘CHICAGO’EXAMPLE 6 （FINDING THE LARGEST AMOUNT OF LOGICAL READS BY QUERY）select buffer_gets， sql_textfrom v$sqlareawhere buffer_gets > 200000order by buffer_gets desc；BUFFER_GETS SQL_TEXT------------------ -----------------------------------------------------------------300219 select order#，cust_no， from orderswhere division = ‘1’Deploying， Managing， and Administering the Oracle Internet PlatformPaper #224/ Page 7GOAL#4： TUNE THE PROBLEM QUERIESA. WHAT YOU NEED TO KNOW BEFORE YOU TUNE YOUR SYSTEMThe first thing you need to know is the data. The volume of data and the distribution of data will affect how youtune individual queries. You also need to have a “shopping cart" full of tuning methods to try. Multiple approachesmust be made to cover all types of queries. A single method of tuning or a single tuning product is not enough. Youalso need to know where the system is slow. Many DBAs and developers spend endless hours finding problemqueries instead of asking the users of the system. Users will almost always be happy to volunteer this information.You also need to network with other developers that work on a similar system. Sharing information at user groups isa great way to network.B. USING “KEY” HINTS FOR OPTIMIZATIONEventually， you will find a query that requires specific tuning attention. When the query is found， you must takeadvantage of the “hints” that Oracle offers for tuning individual queries.FULL - Force a Full Table ScanSELECT /*+ FULL（table_name） */ column1， column2 ……INDEX - Force an Indexed SearchSELECT /*+ INDEX（table_name index_name1 index_name2……） */ORDERED - Force the driving table as in FROM clauseSELECT /*+ ORDERED */ column1， column2 ……FROM table1， table2ALL_ROWS - Explicitly chooses the cost-based approach with a goal of best throughput.Select /*+ ALL_ROWS */ ……FIRST_ROWS - Explicitly chooses the cost-based approach with a goal of best response time.Select /*+ FIRST_ROWS */ ……？ Note： The optimizer ignores this hint in ‘delete’ and ‘update’ statements， and in select statements that contain anyof the following： set operators， group by clause ， for update， group functions and distinct operators.C. THE DRIVING TABLEIn v7， the cost-based approach uses various factors in determining which tables should be the driving table （the tablethat drives the query） in a multi-table join query. The best thing to remember is to realize that you have control overwhich table will drive the query through the use of the ORDERED hint. No matter what the order is from theoptimizer， that order can be overridden by the ORDERED hint. The key is to use the ORDERED hint and vary theorder of the tables to get the correct order from a performance standpoint.select tabA.col_1， tabB.col2from tabA， tabBwhere tabB.col2 = ‘ANL’；select /*+ ORDERED */tabA.col_1， tabB.col2from tabA， tabBwhere tabB.col2 = ‘ANL’；Sometimes the optimizer “goes to lunch”：Rule based explain plan：186 Lines （4 hours）Use of the “ORDERED” HINT：7 Lines （35 sec.）？ By using the ORDERED hint and varying the order of the tables in the FROM clause of the query， you caneffectively find out which driving table is best for your query.D. PARALLEL QUERYOracle‘s parallel query option has opened up a new avenue for performance enhancements. DBAs can now spread aCPU intensive report across many processors， taking advantage of the full speed of the box. You can also use theDeploying， Managing， and Administering the Oracle Internet PlatformPaper #224/ Page 8PARALLEL=TRUE with DIRECT=TRUE with SQL*Loader. On the down side， you can also take down a tenprocessor box with a single query using this. The queries listed below should give you the general syntax and uses forthe PARALLEL hint.EXAMPLE7 （USING THE PARALLEL HINT； PARALLELISM DEGREE IS 4）SELECT /*+ FULL（CUST） PARALLEL（CUST， 4） */ENAME， JOBFROM CUSTWHERE TABLE_NAME = ''EMP''；FUNCTION-BASED INDEXES （ORACLE8I）One of the largest problems with indexes is that the indexes are often suppressed by developers. Developers usingthe UPPER function can suppress an index on a column for a given query. In Oracle8i， there is now a way to combatthis problem. Function-based indexes allow you to create an index based on a function or expression. The value ofthe function or expression is specified by the person creating the index and is stored in the index. Function-basedindexes can involve multiple columns， arithmetic expressions or may be a PL/SQL function or C callout. Thefollowing example shows an example of a function based index.Creating the Function-based IndexCREATE INDEX emp_idx ON emp （UPPER（ename））；An index has been created on the ename column when the UPPER function is used on this column.Query the emp table using the Function-based Index：select ename， job， deptnofrom empwhere upper（ename） = ‘ELLISON’；The function-based index （emp_idx） can be used for the query above. For large tables where the condition retrieves asmall amount of records， the query yields substantial performance gains over a full table scan.？ 8i Tip： Function-based indexes can lead to dramatic performance gains when used to create indexes on functionsoften used on selective columns. See Chapter 13 for additional Oracle8i performance enhancements.To comprehend the advantages of function-based indexes consider the following queries.EXAMPLE8 （USING THE FUNCTION-BASED INDEXES）select count（*）from samplewhere ratio（balance，limit） >.5；Elapse time： 20.1 minutesWe create a functional index.create index ration_idx on sample （ ratio（balance， limit））；We re-run the query using the function-based index.select count（*）from samplewhere ratio（balance，limit） >.5；Elapse time： 7 seconds！！！Note that the function RATIO simply divides argument 1 by argument 2.ORACLE8I： MATERIALIZED VIEWS AND QUERY REWRITEThe combination of Materialized Views and Query Rewrite are power tools for the Oracle data warehouse inOracle8i. Materialized views can be used to create and automatically refresh summary fact tables （the central table ina data warehouse）
用户购买服务器时所需要的，并不是只有硬件，而是包括软件、网络等在内的一个整体系统，这一系统必须根据用户的特点、个性加以设计、部署
利用华赛自研的UltraPath多路径软件，可以实现主机端多条路径之间的冗余互备和负载均衡，有效防止单点故障
在数据集中后，可以选择一个最适合的数据库平台，将新数据存储于此，陆续淘汰其他数据库，最终形成单一的数据库平台
这一部分测试了AF3000在开启快照功能以及重删和压缩功能时的IOPS和延时，测试过程以及最终结果如下
目前华为约有19.7万员工，业务遍及170多个国家和地区，服务30多亿人口
从IBM涉足数据库市场时，它与甲骨文的竞争就已经开始;甲骨文进入管理软件市场，则为自己树立了SAP这样一个强大的竞争对手;当甲骨文收购Sun，它与IBM、惠普的竞争态势也渐渐浮出水面……思科宣布进入企业计算市场，惠普大举杀入网络市场，这也造就了双方的竞争关系
