See the comments and descriptions in :

I have implemented the following:

Global option maxHttpCallPersistentRequests now defaults to 100 - so sockets will be used up to 100 times by default.

A global option @useHttpCallPersistentRequests, which defaults to false, controls whether soapcalls uses persistent connections by default.

If PERSIST has been specified on the SOAPCALL ECL then persistent connections will be used.

If a secret is being used to supply details for the soapcall, then

the value for key "persist" can be used to enable or disable persistent connections
the value for key "persistMaxRequests" can be used to override the default number of times a connection is used.

Secrets take precedence over the ECL syntax, which takes precedence over the default options.