CIFS Server Administrator's Guide Version A.03.02.00 (5900-2578, January 2013)

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.
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.
Constraints
The HP CIFS Server TDB memory map support has the following constraints:
• NOTE: Do not have binaries from mixed versions of mmap and non-mmap daemons/utilities
of CIFS Server in the /opt/samba/bin subdirectory.
• You must use the tdbbackup utility to backup TDB files, do not use the cp command to
backup TDB files.
TDB memory-mapped access for HP CIFS Server 159