Veritas FlashSnap Point-In-Time Copy Solutions 5.0 AdministratorÆs Guide, HP-UX 11i v3, First Edition, May 2008

30 Setting up volumes for instant snapshots
Creating a shared cache object
If the cache space becomes exhausted, the snapshot is detached and marked as
invalid. If this happens, the snapshot is unrecoverable and must be removed.
Enabling the autogrow feature on the cache helps to avoid this situation
occurring. However, for very small caches (of the order of a few megabytes), it is
possible for the cache to become exhausted before the system has time to
respond and grow the cache. In such cases, use the
vxcache command to
increase the size of the cache, or to reduce the value of highwatermark.
If necessary, you can use the vxcache set command to change other autogrow
attribute values for a cache. For example, you can use the maxautogrow
attribute to limit the maximum size to which a cache can grow. To estimate this
size, consider how much the contents of each source volume are likely to change
between snapshot refreshes, and allow some additional space for contingency.
Caution: Ensure that the cache is sufficiently large, and that the autogrow
attributes are configured correctly for your needs.
See the
vxcache(1M) manual page and the “Administering Volume Snapshots”
chapter in the Veritas Volume Manager Administrator’s Guide for more
information including how to grow, shrink and remove a storage cache.