8.47 DEFSTORE (Display or define main and expanded storage
values)
8.47.1 Function
The DEFSTORE command is used to specify the size of the main and expanded storage. Given without
an argument the DEFSTORE command displays the current size of the main and expanded storage. If
only the type of storage is given, the current storage size of this type is displayed. Storage is allocated in
megabytes, unless a specific unit is specified. The actual upper limit of the main and expanded storage is
determined by the host system's architecture, operating system, and on some systems the amount of
physical memory and paging space you have available.
The practical limit depends on the maximum amount of storage that can be obtained by the “malloc”
function (usually around 1 GB on 32-bit platforms; on 64-bit platforms the value should only be limited by
available paging space).
When increasing the storage size Hercules attempts to allocate first the new storage. If the new allocation
is successful then the previously allocated memory will be freed. This is to prevent a situation where the
old memory is freed first, then the new allocation fails and a reallocation of the memory in the previous
size also fails because of storage fragmentation and therefore leaving Hercules without memory.
When decreasing the storage the memory will stay allocated in the previous size but the storage size will
appear as decreased. Subsequent increases will not reallocate memory unless they go over the already
allocated amount.
An additional optional argument determines the locking state of the allocated memory (page lock by host
operating system). The LOCKED option indicates that the memory is to be locked into storage while UN-
LOCKED (the default) indicates that the memory is not locked into the storage.
Please note that Hercules preserves the last locking state of DEFSTORE for each type of storage. Once
the storage is locked, any subsequent change to the storage size will honor the existing lock state of me-
mory unless the lock state is specified again on the DEFSTORE command.
Caution: Do not lock storage unless sufficient real memory is available to back up the request. Failure to
do so may require the host system to be rebooted.
8.47.2 Syntax
Descriptive
msize[ ] [
xsize[ ] [
Diagram
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