CF cache structure, which is a structure in the CF that contains a directory
to keep track of data that is shared among cache users. z/TPF systems that are
connected to the CF cache structure can manage
shared data.
Permanent storage, which is storage that is the final repository
for the data that z/TPF systems share and might be on DASD. z/TPF systems can read
the data from permanent storage to local cache buffers and use the
directory-only caching method to track the validity of the data. After z/TPF systems make updates
to the locally cached data, they are responsible for ensuring that
the changes are made to the permanent storage copy of the data. They
make these changes to permanent storage either immediately after the
update or at a later time depending on the cache protocol. See z/TPF Application Programming for more information
about permanent storage and the relationship to logical record caches.
Local cache buffers, which are buffers that z/TPF systems allocate
in their own storage area. They contain copies of data that is shared
among cache users. z/TPF systems read data
from permanent storage to their local cache buffers and write data
from their local cache buffers to permanent storage. Each z/TPF systems that accesses
the CF cache structure must have a set of local cache buffers to accommodate the data to
be shared. See z/TPF Application Programming for more information about local cache buffers and their
relationship to logical record caches.
Local cache vector, which is a vector that provides a way
for CF cache users to determine if data in their local cache buffers
is valid. There is one local cache vector for each z/TPF system using the
cache. Each vector is divided into separate entries with each entry
corresponding to a local cache buffer. Each vector entry contains
an indicator that the CF sets to indicate whether the data in the
corresponding local cache buffer is valid.
The z/TPF system supports processor unique caches and processor shared caches:
Processor unique cache contains cache entries that are
used by only one processor in a loosely coupled complex.
Processor shared cache contains cache entries that are
kept synchronized between all processors in a loosely coupled complex that
are using the cache.
Figure 1 shows the elements and their
relationship to each other for a processor shared cache. Each piece
of shared data can be stored in different locations in the cache system.
Copies of shared data are stored in the local cache buffers (fastest
access) belonging to each cache user. The shared data also resides
on permanent storage (slower access to the data than from the local
cache). In general, how quickly you access the data depends on where
it is stored. Figure 1. Elements of a cache system for
processor shared cache
Figure 2 shows the elements and their
relationship to each other for a processor unique cache. Figure 2. Elements of a cache system for processor unique cache
