DEFINE STRUCTURE keywords and parameters

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.