HP CIFS Server 3.0f Administrator's Guide verison A.02.03

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 provides 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 v1, 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"
To resolve the above errors, you must increase the value of fixed mmap size in smb.conf
accordingly and then restart the HP CIFS Server.
• Memory-mapped access fails when the system is low on memory resources. In this case, the HP CIFS
Server will terminate the connection and log the following error messages:
"ERROR. Abort due to munmap failure."
"ERROR. Abort due to tdb_mmap failure."
To resolve the above errors, you can turn off the memory map feature by setting the value of use mmap
to no and then restart the HP CIFS Server.
168 HP-UX Configuration for HP CIFS