JR43804: CMVC 223884 - TO HAVE THE CACHE ENTRIES IMPLEMENT SIZABLE

7.0.0-WS-WCServer-FP009

APAR status

• Closed as program error.

Error description

• WebSphere Application Server DynaCache provides the capability
  to limit the size in megabytes of each cache instance.
  This feature is available by implementing the
  com.ibm.websphere.cache.Sizeable Java interface.
  Cache entries used by WebSphere Commerce do not implement this
  interface.
  The result is that this capability cannot be used, and the Cache
  Monitor application shows the size of each cache entry as -1
  (disabled).
  

Local fix

Problem summary

• USERS AFFECTED:
  Any user wishing to use the memoryCacheSizeInMB in
  cacheinstances.properties for data cache
  
  PROBLEM ABSTRACT:
  WebSphere Commerce does not give the option to limit memory
  cache size
  
  BUSINESS IMPACT:
  Currently, without this feature, customers can limit the size of
  each cache instance by the maximum number of cache entries that
  can be contained in memory, and by the maximum size of the disk
  cache in gigabytes, but they cannot limit the memory footprint
  by specifying a maximum number of mega-bytes.
  To properly plan and configure each cache instance to avoid
  excessive memory footprint, they must run simulation tests,
  obtain heapdumps, and estimate the correct maximum size in terms
  of number of entries based on the observed memory footprints.
  
  RECOMMENDATION:
  

Problem conclusion

• This iFix implements the com.ibm.websphere.cache.Sizeable
  interface for most cache entries used by WebSphere Commerce.  In
  particular, it does so for cache entries in the following
  DistributedMap object caches:
  
  services/cache/DM_Cache (Marketing cache)
  services/cache/DM_UserCache (Marketing user behavior cache)
  dmap/IVCache (External Inventory availability cache)
  dmap/PriceCache (External Price cache)
  services/cache/WC*DistributedMapCache (all the "data cache"
  object cache instances)
  
  It also implements the Sizeable interface for most cacheable
  commands used by WebSphere Commerce "out of the box".
  
  This iFix does not implement the Sizeable interface for the
  Price Rule cache, nor does it do so for Sales Center cacheable
  commands.
  
  For backward compatibility, this capability is not enabled "out
  of the box" and must be explicitly configured in the
  CrossTransactionCache tag of the InstanceProperties tag in the
  wc-server.xml instance configuration file.  A new "sizeable"
  property is defined for the CrossTransactionCache tag:  specify
  sizeable="true" to enable this capability.
  
  A cache entry that implements the Sizeable interface provides an
  estimate of its memory footprint to DynaCache, allowing
  DynaCache to control the overall memory footprint of each cache
  instance.  Test results have shown that the accuracy of the
  estimate can vary.  Observed estimates for the above object
  caches were generally slightly higher than their actual memory
  footprint.
  
  Note:  DynaCache will disable this capability for a cache
  instance if it detects that a cache entry that does not
  implement the Sizeable interface (for example custom cacheable
  commands in the baseCache) is placed into a cache instance.
  When this happens, a message like the following is placed in the
  SystemOut.log:
  DYNA1067E: The cache size in MB feature is disabled because the
  cached object is not sizeable.
  
  Note:  While DynaCache automatically implements the Sizeable
  interface for servlet (JSP) cache entries, test results have
  shown that the sizes calculated for these entries can be
  significantly underestimated.  For example, in some tests the
  actual memory footprint of the baseCache servlet cache was
  observed to be significantly larger than the calculated memory
  footprint reported by the cachemonitor application.  For these
  reasons, it is generally not advised to specify the memory size
  in MB for servlet cache instances.
  
  Note:  The normal cache maximum size setting is also used to
  limit the number of cache entries kept in memory.  You should
  continue to specify a reasonable maximum size setting for each
  cache instance, to control the memory footprint and prevent
  potential out of memory conditions.
  -------------------------------------------------------------
  The latest available maintenance information can be obtained
  from the Recommended Fixes for WebSphere Commerce technote:
  http://www.ibm.com/support/docview.wss?rs=3046&uid=swg21261296
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  WC BUS DEV ED W

• Fixed component ID

  5724I3900

Applicable component levels

• R700 PSY

     UP