Hi Rick
Based on my experience Selection table (S Table) which usually has name like /1APO/S**000**. This is a selection table and gets created for individual planning area in system. Read the selection id which has flag "A" (Alert Monitor) This is the table from which gets the details of Agg levels/selections for which alert is generated.
Besides you can try these SE38 programs to access selection from that table - /SAPAPO/MCPSH_GEN_SELTAB_SE16 and /SAPAPO/MCPSH_GEN_SELTAB_MGM
Additionally please spend some time on this program /SAPAPO/AMODAL_DELETE to find out where it is reading data related to database alerts. This will help you find out table names other than /SAPAPO/AM_ALERT.
Please do share details upon finding the solution
Thank you
Satish Waghmare