The command SET DATABASE PARAMETER allows you to modify, for the current process, a variety of internal parameters of the 4D database. There is an example database available that illustrates some uses of this command:

"Structure Access" Example Database

Here are brief descriptions of the available selectors along with links to related information, for complete information see the 4th Dimension Language Reference:

Seq Order Ratio
Ratio between the number of selected records and the total number of records below which the sorts execute in sequential mode.

Seq Access Optimization
Optimization mode for sequential accesses such as sort, search or selection to array. In optimized mode, 4D will read numerous records at a time from the disk but will not place them in the cache.

Seq Distinct Values Ratio
Ratio between the number of selected records and the total number of records below which the DISTINCT VALUES command will execute in sequential mode
See also the Elements of Successful Arrays tech note.

Index Compacting
This selector allows you to enable or disable the compacting of index pages.
See also the tech tip Compacting Index Pages in 4D's Memory Cache.

Seq Query Select Ratio
Ratio between the number of selected records and the total number of records below which the QUERY SELECTION command will execute in sequential mode.
See also the tech tip Optimizing QUERY SELECTION With a Small Current Selection.

Minimum Web Process / Maximum Web Process
Minimum and maximum number of Web processes to maintain for Non-contextual Mode.
See also the tech tip Web Server Optimization using SET DATABASE PARAMETER.
See also Web Services, Web Connection Processes.

Web conversion mode
By default, in Contextual Mode the 4D Web Server 6.7 uses the cascading style sheets (CSS1) to generate HTML pages similar to the 4D forms displayed in 4th Dimension. With this feature, the forms might not convert correctly for databases created with previous versions of 4D. Consequently, you have the possibility to set the form conversion mode to that used in a previous version of 4D.
See also Web Services, HTML Support.

4th Dimension Scheduler / 4D Server Scheduler / 4D Client Scheduler
Allows you to set the CPU utilization of 4D products.
See also the tech tip How to set the CPU utilization in 4D version 6.7.

4D Server Timeout / 4D Client Timeout
This parameter allows changing the value of the 4D Server and 4D Client timeouts.
See also the tech tip Client/Server Connections Timeouts in Detail.

Port ID / IP Address to listen
This parameter allows to change on the fly the TCP port ID and IP Address upon which the 4D Web Server is listening. These selectors are useful for compiled and merged 4D Web Servers, in which there is no way for users to access the Design mode.
See also Web Services, Configuration.
See also Web Services, Web Server Settings.

Character set
This parameter allows user to change on the fly the character set that the 4D Web Server should use to communicate with browsers connecting to the database. This selector is useful for compiled and merged 4D Web Servers, in which there is no way for users to access to the Design mode.

Max Concurrent Web Processes
This parameter allows setting the high limit of concurrent Web processes of any type supported by the 4D Web Server. When the limit is reached, 4D will not create any more processes and instead returns HTTP status 503 - Service Unavailable.
See also Web Services, Web Server Settings.