SLM Cluster
As described previously, the SLM Cluster can keep track of the licenses of several Infor applications. You can install the SLM server of an SLM Cluster on the same host as the adopting application or install this SLM server on a central host if multiple applications spread over several machines are licensed.
If you have multiple applications using SLM for license validation it is recommended to install at least two SLM Servers on different hosts. These two will together make one SLM Cluster.
Installing multiple SLM servers which are configured to form one SLM Cluster is mainly used for high availability of the SLM service.
The license information of the SLM Cluster is managed through the SLM MMC snap-in. When you manage an SLM Cluster, the MMC snap-in automatically identifies the master server within that cluster responsible for maintaining the license configuration data.
SLM Cluster Concept
This section describes the concept of SLM Clusters and the installation of multiple SLM servers.
An SLM Cluster is a group of one to four SLM servers that act as one license manager. Having more than one SLM Server in an SLM Cluster is intended to handle fail-over situations and to support large quantities of license requests. If one SLM server stops, the other servers of the group can take over.
Always one and only one SLM Server in an SLM Cluster has to run in master mode. You must mark one of the SLM servers in a cluster in Master mode, and the other SLM Servers as slaves. By default the first SLM Server installed will act as master server the additional servers added later as slaves.
All servers in an SLM Cluster will handle license requests; the additional role for the master server is to be the owner of the license configuration. The slaves retrieve their configuration data from the Master SLM server.
The SLM clients spread their license requests over the various SLM servers.
Fail over
If one or more SLM servers in a group fail to operate, the other servers in the group will take over. The following example illustrates just how the SLM servers backup each other:
Suppose your adopting application is licensed with 100 concurrent user licenses and you are working with an SLM Cluster of four SLM servers: SLM servers A, B, C, and D.
The license distribution for that application at a particular moment when all SLM servers are available can be as follows:
| Server | Claimed licenses |
|---|---|
| A | 30 |
| B | 30 |
| C | 20 |
| D | 20 |
| Total | 100 |
Suppose SLM server A fails to operate because the server is stopped or the machine on which this server operates is decoupled from the network. The other SLM servers in the group will notice the failure of SLM server A and distribute the current 30 claimed licenses among each other, depending on the requests from the SLM clients. The total amount of concurrent licenses remains 100 concurrent licenses.
The total of 100 remains for a limited period of time, called the grace period. That grace period is specified as 72 hours.
This table shows the distribution of claimed licenses during this grace period:
| SLM server | Claimed licenses |
|---|---|
| A | Failed |
| B | 40 |
| C | 25 |
| D | 35 |
| Total | 100 |
If the failing SLM server is not running again after that grace period, the total number of licenses decreases in proportion to the percentage of the failed servers in the group. In this example, this implies that the total number of licenses will be lowered by 25 percent to 75 percent, because SLM server A represents 25 percent of the group.
This table shows the distribution of claimed licenses after the grace period:
| SLM server | Claimed licenses |
|---|---|
| A | Failed, grace period elapsed |
| B | 30 |
| C | 25 |
| D | 20 |
| Total | 75 |
To return to the total number of 100 licenses, you can perform one of these actions:
- Bring SLM server A to life again.
- Delete the SLM server A from the group and revalidate the group with Infor Validation. You will now have one SLM Server less.
- Delete the SLM Server A from the group and add another SLM server E in this group and revalidate that group with Infor Validation.
High availability support
In some instances, Infor can grant customers high availability support. To prevent a particular percentage of your licenses from being lowered after the grace period, you must select the High Availability Support (HAS) option in your SLM server configuration.