What is the definition of an inactive connection?
A connection is inactive, if it currently does not execute any RFC-enabled function module in the SAP system.
and what can cause this when establishing connection with SAP?
Well, it’s caused by the IS not wanting to execute anything in the SAP system at the moment… There’s no need to keep these connections open forever, so in order to release the network resources, the SAP Adapter closes these idle connections. If at a later time new RFC requests are to be sent into SAP, the connection pool opens new connections again.
Basically this parameter allows you to define, for how long the SAP Adapter should keep idle connections open before cleaning them up. If you know, that the RFC requests come in “waves”, e.g. a couple dozen at the same time and then nothing for the next 30min and then the next couple dozen, it maybe good to set the timeout to 31min in order to improve performance. However, if you only have a request once every couple hours without a regular pattern, it maybe better to set the timeout to 1 min and have the network connections released right away, instead of keeping them open for hours needlessly.