TSM Expiration Rate

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The TSM Expiration Rate is the number of TSM Objects expired in a given time period. It is not the number of objects examined, which would be far higher. IBM recommend that the Expiration Rate be greater than 3800000 objects per hour. The following TSM SQL query will print the expiration rate for recent expiration runs:

select activity, -
  cast ((end_time) as date) as "Date", -
  (examined/cast ((end_time-start_time) seconds as decimal (18,13))*3600) "Obj/Hr" -
from summary -
where activity='EXPIRATION' and days (end_time) - days (start_time) = 0

To improve the expiration rate, there are several points to keep in mind:

  • expiration is a single thread, from a processor perspective
  • on a system with fast enough CPUs, expiration quickly becomes I/O bound, generating random I/O to the database volumes
  • a high cache hit percentage is critical to obtaining a high expiration rate

Misinformation found herein copyright Paul Ripke (aka “stix”) stixpjr@gmail.com.