The DEFINE STRUCTURE specification requests that an entry for a
coupling facility structure be defined in the LOGR policy for a coupling
facility log stream. The keywords are explained as follows:
- NAME(structname)
- Specifies the up to 16-byte name of the coupling facility structure
you are defining. NAME must be 16 alphanumeric or national ($,#,@)
characters, or underscore (_), padded on the right with blanks if
necessary. The first character must be alphabetic.
- LOGSNUM(logsnum)
- Specifies the number of log streams that can be allocated in
the coupling facility list structure that is being defined. Note that
this is the number of logstreams in the structure, not the number
of connections to the structure. logsnum must be a value
between 0 and 512.
LOGSNUM is required when defining a structure.
- MAXBUFSIZE(maxbufsize)
- Specifies the size, in bytes, of the largest log block that
can be written to log streams allocated to the coupling facility specified
in this request.
The value for MAXBUFSIZE must be between 1 and
65532 bytes. The default is 65532 bytes.
- AVGBUFSIZE(avgbufsize)
- Specifies the average size in bytes, of log blocks written to
all the log streams using this coupling facility structure.
System
logger uses the average buffer size to control the entry-to-element
ratio for this coupling facility structure.
When
the active primary LOGR couple data set is at an OS/390® Release
3 level or higher, system logger uses the AVGBUFSIZE specified
simply to make an initial determination of the entry-to-element ratio
for the structure. After that, system logger monitors structure usage
and dynamically manages the entry-to-element ratio accordingly. System
logger uses the last entry-to-element ratio in effect for a structure
for subseqent structure reallocation requests.
When
the active primary LOGR couple data set is at a pre-OS/390 Release
3 level, system logger uses the AVGBUFSIZE specified to calculate
an entry-to-element ratio that lasts for the life of this coupling
facility structure. You cannot update the average buffer size for
a structure without first deleting the structure definition (and all
the log stream definitions associated with the structure) and then
redefining the structure with a new average buffer size.
The avgbufsize must
be between 1 and the value for MAXBUFSIZE. The default value is 1/2
of the MAXBUFSIZE value.