#!F-adobe-helvetica-medium-r-normal--18*
#!N 
#!CDarkGreen #!N  #!Rall571 Data Explorer Object 
Cache #!N #!EC #!N #!N Data Explorer uses an object cache 
to store intermediate results of modules. Caching systems are intended to 
fill up and then reclaim memory by throwing things out of 
the cache. The size of the cache defaults to a large 
percentage of the physical memory on the machine. You can control 
the size of the cache with the -memory command line option 
to the  #!F-adobe-times-bold-r-normal--18*   dx #!EF command. The minimum cache size needed 
is on the order of the maximum amount of memory required 
for a program execution. #!N #!N The Data Explorer "executive" schedules 
module execution. It does detailed graph analysis, implements distributed processing of 
the modules, and implements the Switch and Route modules. It also 
provides optimization by caching the intermediate outputs of modules. For example, 
if you run Import twice in a row with the same 
inputs, Import will not actually run the second time, and instead 
the executive will use the cached output from the previous execution. 
The Image and Display tools also cache their images internally. #!N 
#!N To implement the caching scheme, Data Explorer will allocate memory 
up to some fixed size. This memory is referred to as 
the arena. When the arena fills up and more memory is 
required, Data Explorer looks for objects to discard from the cache. 
When it does this it may mean that subsequent executions will 
have to execute larger portions of the program. #!N #!N The 
arena is of fixed size for any one instance of Data 
Explorer. The size of this arena is chosen by default based 
on the size of the physical memory in the system. For 
some data sets, the default arena size will not be sufficient. 
In those cases, one can use the -memory option to increase 
the size of the arena, with the limitation that your can't 
increase the arena size to be larger than the amount of 
real plus virtual memory (page or swap space) on your machine. 
Talk to your system administrator if you think you need to 
increase the amount of swap space on your system. #!N #!N 
#!N  #!F-adobe-times-medium-i-normal--18*   Next Topic #!EF #!N #!N  #!Lall572,dxall573 h Reducing Memory Requirements  #!EL  #!N  #!F-adobe-times-medium-i-normal--18*   #!N 

