HP CIFS Server Administrator's Guide (5900-1282, April 2011)

NOTE: To modify the value of use mmap or fixed mmap size, you must first stop all of the
CIFS Server processes (smbd, nmbd and winbindd daemons), modify the settings of the parameters,
and then restart the CIFS Server processes. It is not safe to modify the memory map settings using
a procedure other than the one mentioned above.
Mostly Private Address Space (MPAS) Support on HP-UX 11i v2 IA and 11i v3 IA
systems
HP CIFS Server A.02.03 and A.03.01a provide MPAS enhancement to support memory-mapped
access of all TDB files on HP-UX 11i v2 IA amd 11i v3 IA systems. With this functionality, each
process uses a private, process-specific address. Because of address aliasing, many private
addresses can point to the same file, this will ensure memory-mapped access for all CIFS Server
processes. To enable the memory-mapped access functionality, set the smb.conf use mmap
parameter to yes. The default value of use mmap is yes.
NOTE: To modify the value of use mmap, you must first stop all of the CIFS Server processes
(smbd, nmbd and winbindd daemons), modify the setting of the parameter, and then restart the
CIFS Server processes. It is not safe to modify the setting of use mmap using a procedure other
than the one mentioned above.
Unified File Cache Support on an HP-UX 11i v3 system
The unified file cache is an HP-UX file system feature that integrates the page cache and buffer
cache to provide coherency for file access. In case of memory-mapped failures such as low on
memory resource or exceeding the fixed memory map size, HP CIFS Server for HP-UX 11i v3 IA
supports fall back to file I/O operations on all TDB files. HP CIFS Server for HP-UX 11i v3 PA
supports fall back to file I/O operations only on the memory-mapped TDB file, locking.tdb.
On HP-UX 11i v2 PA and 11i v2 IA, HP CIFS Server does not support TDB file I/O fall back
operations. In case of memory-mapped failures, it will result in termination of the connections.
HP CIFS Server supports HP-UX unified file cache functionality for memory-mapped access of Trivial
Database (TDB) files on HP-UX 11i v3 PA and IA systems. The unified file cache is an HP-UX file
system feature that integrates the page cache and buffer cache to provide coherency for file access.
Without the unified file cache support, the file system uses the buffer cache to cache file data and
the memory-mapped access of files uses the page cache to cache file data. If an application
accesses the file using both read()/write() system calls and memory-mapped access simultaneously,
no coherency is guaranteed between these two caches. With the unified file cache support,
coherency can be achieved.
What to Do if You Encounter Memory Map Error Messages
This section includes information about memory map error messages and actions you may take as
follows:
• The HP CIFS Server will terminate the connection and log the following error messages, in the
event that the value of fixed mmap size is not sufficient:
"tdb_expand: ERROR. Requested size (%d) > fixed mmap size (%d).
Please increase the value of "fixed mmap size" option then restart
CIFS Server"
"mmap_if_required: ERROR. "fixed mmap size" parameter must be at
least 8192 bytes.\n"
152 HP-UX Configuration for HP CIFS