Shulou(Shulou.com)05/31 Report--

In this issue, the editor will bring you five principles and four suggestions about the use of implicit parameters in Oracle database. The article is rich in content and analyzed and described from a professional point of view. I hope you can get something after reading this article.

The implicit parameter is the parameter prefixed with "_" in the database parameter name, which cannot be obtained through a simple show parameter/spparameter query without a clear set value. It has the following principles of use:

1. Implicit parameters can not cover all problems, nor can they solve all problems

2. Just solve the workaround of a particular scene

3. It must be tested and verified in the test environment before it can be used in the production environment

4. due to the application's own characteristics and non-common problems, it is not recommended to popularize.

5. It is recommended to use it after being confirmed by the original engineer of oracle.

The base table related to the implicit parameters can be found through the 10046 tracking method:

As shown in the figure above, you can see that there are two base tables starting with x$, namely x$ksppi (Kernel Service Parameter Parameter Information) and x$ksppcv (Kernel Service Parameter Parameter Current Value). The two base tables basically contain all the database implicit parameters.

The descriptions of the two base tables are as follows:

The method of getting implicit parameters (variables are entered by themselves in & name):

Select a.ksppinm name,b.ksppstdf default_on,b.ksppstvl value,a.ksppdesc description from x$ksppi an and a.ksppinm like ksppcv b where a.indx=b.indx and substr (a.ksppin 1) ='_ 'sppcv% & name%' order by a.ksppinm

In the database version of 11.2.0.4.8, there are more than 2500 implicit parameters, and the number of implicit parameters in each database version may vary, and even some implicit parameters have different default values in different versions, which requires special attention.

For example, if there is the word ADG in the parameter, through the SQL query, the implicit parameters related to ADG are roughly judged as follows:

The classification of the use of implicit parameters is roughly as follows:

Assist in problem analysis

Functional characteristic control switch

Threshold size setting adjustment

Emergency handling and manual control

Based on the experience of database design and long-term operation and maintenance, some of the implicit parameters recommended are as follows:

When you modify the setting of an implied parameter, you need to enclose the parameter name in double quotes to the left of the equal sign and use the alter statement to change it, or modify it directly in the pfile parameter file.

In summary, the description of the implied parameters is summarized as follows:

1. If you can solve the problem in a simple way, don't complicate it.

2. Any implied parameters should be set carefully

3. It is necessary to fully understand the characteristics of the implied parameters before using.

4. For new features to be enabled, it is recommended to evaluate the characteristic mechanism of relevant implied parameters.

These are the five principles and four suggestions for the implicit parameters of Oracle database shared by the editor. If you happen to have similar doubts, please refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

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