Draft Document for Review February 7, 2020 3:15 pm 8464ch10_OperSW.fm 10.3 Expire Hold and scratch processing considerations 10.3.1 Expire Hold and low on scratch volumes 10.3.2 Expire Hold and cache utilization in a TS7700D This section describes the interaction between SCRATCH processing and the Expire Hold  setting for scratch categories on the TS7700. For more information about the Expire and  Expire Hold options for a category and the conditions that must be met for a volume that is  assigned to the category to be delete-expired, see “Defining scratch categories” on page 553.  When Expire Hold is set for a scratch category, it can heavily affect scratch volume  availability. Consider the following cases: The Expire Hold option is used to ensure that a virtual volume that is sent to the SCRATCH  pool cannot be reused or deleted before the grace period that is specified as the EXPIRE time  passes. This fact can create a problem where the library might run out of available volumes to  satisfy mount requests to write new data.  If the EXPIRE time is set too long and not enough virtual volumes are released to keep a  healthy level of SCRATCH volumes available, it might be necessary to reduce the EXPIRE  time.  However, this change affects only new volumes that are going into the SCRATCH pool. The  existing volumes in the pool continue to be held until the original EXPIRE time passes.  However, if Expire Hold is cleared, these volumes can then be added to the candidate list for  SCRATCH mounts. Therefore, clearing the Expire Hold option immediately helps to alleviate  the low on scratch condition, but it no longer protects data that inadvertently was sent to  SCRATCH. The recovery of user data on volumes in the SCRATCH pool might no longer be  certain. When the Expire Hold option is enabled, the cache in a TS7700 is used up in part by holding  data from virtual volumes that were sent to the SCRATCH pool. In addition to the risk of  running out of virtual volumes to mount, a risk exists of running out of cache in a TS7700D  when AUTOREMOVAL is not enabled.  Again, consider EXPIRE time. If a TS7700D is consistently running high on cache usage,  adjust this EXPIRE time. In this case, clearing the Expire Hold setting does  not  immediately  alleviate the high cache usage condition. The effect of disabling the Expire Hold from the  cache perspective is to enable volumes in the SCRATCH pool to begin entering the candidate  list for expire delete processing.  A task runs in the library once per hour that processes some number of volumes from this list  and reduces cache usage by deleting the expired volumes from cache. The number of  volumes that are deleted per hour by default is 1000.  The number of volumes that are moved to this candidate list is customizable (1000 - 2000),  and is controlled by using the following command: LI REQ,composite-library,SETTING,DELEXP,COUNT,value  Chapter 10. z Host Console operations  611 GLYPH<SM590000> Expire Hold option is enabled and the TS7700 is low on scratch volumes GLYPH<SM590000> Expire Hold option is enabled and Cache Utilization is beyond the wanted threshold in the  TS7700D.