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Subsections
The class ss_m is the core of the SSM interface. Creating an
instance of ss_m starts the SSM. Destroying the ss_m
instance causes the SSM to shutdown. Details on initialization and
shutdown are available in init(ssm).
When the SSM is started, it processes configuration options described
below and initializes all the SSM data structures. This
initialization includes allocation of the buffer pool. The buffer pool
is located in shared memory, so the operating system must have
shared-memory support to accommodate the size of the buffer pool.
Next, the SSM checks the log to see if recovery is needed.
If so, it follows the steps discussed in
the recovery section below.
The SSM has several configuration options that must be set before
it is started with the ss_m constructor.
These options include such things as buffer pool sizes and location
of the log. Many have default values. Those without default
values must be set or the SSM will fail.
- sm_bufpoolsize
- no-default
The size of buffer pool in K-bytes. The minimum value is 64.
Increasing the size may decrease the amount of I/O done by the SSM.
- sm_logdir
- no-default
The SSM currently uses Unix files for log storage. This option sets
the path name of the directory where log files will be placed.
- sm_logsize
- 10000
The maximum size, in K-bytes, of the log. All updates
by transactions are logged, so the log size puts a limit
on how much work any transaction can do. See
the section on logging
for a discussion of log space usage.
- sm_logging
- yes
This options controls whether or not logging is performed at all.
Turning it off, by setting it to no, is used primarily for
evaluating logging performance. No recovery or transaction rollback
can be performed if logging is off.
- sm_diskrw
- diskrw
The path name (in the Unix file system) of the program forked by the SSM to
perform asynchronous I/O, normally SHROOT/bin/diskrw.
- sm_locktablesize
- 64000
The number of buckets in the hash table used by the lock manager.
- sm_backgroundflush
- yes
This option controls whether or not there is
a background thread started to
flush the buffer pool periodically.
- sm_errlog
- - (stderr)
The location to send error logging messages. The
default is the standard error file. Other options
are syslogd (to syslog daemon), or to a specific filename.
- sm_errlog_level
- error
The level of error logging detail.
Possible values (from least amount of logging to most amount)
are none emerg fatal alert internal error warning info debug.
A VAS will often have options of its own that need
to be set. The SSM provides an options facility,
options(common) for this purpose.
Included with the option facility are functions to set options from
the program command line and from files containing configuration
information.
A discussion of how to use the options facility is included in
Configuration Options section of the
VAS Tutorial.
Next: Storage Facilities
Up: The Shore Storage Manager Interface
Previous: Introduction
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10/27/1997