标签：index 11g review memory query Oracle table might select
This is about Oracle database 11g query slow probing.
There was a case about a query took 5 seconds on a 1 million records table.
This looks slow in query performance. There could be many reasons to cause this type of issue, such as disk i/o failure, network latency, or table index.
Let us use table index as an example:
First, we need to check database server's resources, like CPU, memory, or disks. Do we have enough resources when the query is running?
Secondly, we might want to check if the table spaces are running out.
Third, we need to find out which indexes are used when query is running.
stage#1: we might want to try following:
select index_name from user_indexes where table_name ='xxx_DUMP';
alter index my_suspicious_index monitoring usage;
select * from v$object_usage;
select count(*) from xxx_dump order by 1;
This way, we are able to identify the index we are interested are indeed used.
stage#2: validate structure
analyze index my_suspicious_idx validate structure;
select pct_used from index_stats where name='my_suspicious_idx';
We may also apply 'set autotrace' to understand query execution plan. If 'TABLE ACCESS FULL' is found, we might have a clue on how the issue could be resolved quickly. Eventually, we identified the index was the issue, we may want to have the troubled index rebuilt.
To understand why a query took longer time than expected is difficult because there are many reasons behind.
In order to have a full view why this happens, investigation is required, and more time is in need.
In-memory technology might be considered as a short cut in one of Oracle solutions. The idea is simple, which add heavily used tables into the memory to speed up the full table access. It is clear that this solution takes memory, and the In-memory is available in 12C forward.
标签：index,11g,review,memory,query,Oracle,table,might,select 来源： https://www.cnblogs.com/zwang562020/p/15755412.html
本站声明： 1. iCode9 技术分享网（下文简称本站）提供的所有内容，仅供技术学习、探讨和分享； 2. 关于本站的所有留言、评论、转载及引用，纯属内容发起人的个人观点，与本站观点和立场无关； 3. 关于本站的所有言论和文字，纯属内容发起人的个人观点，与本站观点和立场无关； 4. 本站文章均是网友提供，不完全保证技术分享内容的完整性、准确性、时效性、风险性和版权归属；如您发现该文章侵犯了您的权益，可联系我们第一时间进行删除； 5. 本站为非盈利性的个人网站，所有内容不会用来进行牟利，也不会利用任何形式的广告来间接获益，纯粹是为了广大技术爱好者提供技术内容和技术思想的分享性交流网站。