A SQL Server logs-only set has to be used in pair with a VSS-Aware for SQL Server set in order to protect properly a database configured with full or bulk-logged recovery model. For such databases, logs must be backed up separately since they are not truncated (it's a limitation of vss-aware sets that they can only take full or differential backups). Alternatively the second backup set that performs full database backups can be also a SQL Server set (traditional).
An example would be to run a full backup with the VSS-Aware set once a day at 1 am and to run hourly backups for the logs-only set between am and 11:59 pm, so each set will have its own schedule and retention.

The SQL Server logs-only sets will backup during each session one file per database,, e.g. during the first backup session a file called dbname.log00000011 is backed up, in the second session a file called dbname.log00000012 is backed up, and so on, basically the files backed up in a certain session never change, there will be only one generation online for them, in order to have these logs deleted by retention when you do not need them anymore you have to use a retention rule with the following configuration:
- in the first screen of the new retention rule wizard tick 'Time-based retention';
- in the second screen:
 a) set to 0 Keep most recent generations option
 b) tick 'Keep all generations for the last ...", for example 'Keep all generations for the last 1 month' if you configure the retention rule for the VSS-Aware set to keep restore points up to a month, basically you need to cover the oldest generation that will be kept for the set that takes the full dumps.

Following the example above, the retention rule for the SQL set taking the full dumps can be:
- in the first screen of the new retention rule wizard tick 'Time-based retention';
- in the second screen set:
 a) set to 1 Keep most recent generation option
 b) tick 'Keep all generations for the last one month"
You can have different details to this retention concerning the full dump backup, you only need to identify the oldest generation that will be kept so that you configure properly the logs-only set retention (keep all generations for the last .... detail).