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Monitoring log stream interim storage consumption z/OS MVS Setting Up a Sysplex SA23-1399-00 |
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System logger internally tracks the usage of the log stream interim storage medium. Starting at z/OS® V2R1, key information can be revealed to both the installation and exploiter, depending on the configuration of IXGCNF and log stream parameters. This information can assist in exposing offload inhibitors, including those inhibitors which may not trigger logger offload or task monitoring alerts – such an abnormal DASD I/O delays. There are different sets of system logger parameters that affect the level of monitoring for a log stream on a given z/OS system. The first set of parameters to configure are in the log stream definition in the LOGR policy. They are the WARNPRIMARY and HIGHOFFLOAD parameters. System logger establishes an imminent threshold for each log stream based on an interim storage usage percentage above HIGHOFFLOAD. The imminent threshold value is 2/3rd of the difference between 100% full and the HIGHOFFLOAD value. The WARNPRIMARY parameter indicates whether warning messages for this log stream should be issued when the imminent threshold is reached or a 90% entry full condition is encountered for structure based log streams. The default WARNPRIMARY value is NO. These parameters have the following effects:
The system logger alert messages remain in the retrievable messages
list until the appropriate circumstances occur for each:
The second set of parameters allows these messages to be enabled or disabled on a z/OS system basis. This is done through the IXGCNF CONSUMPTIONALERT parameter. The default setting for this parameter is ALLOW, and the interim storage usage alert messages will be issued at the previously described points. When the parameter is set to SUPPRESS, it indicates that no interim storage warning messages will be issued, regardless of the log stream parameters. Additionally, XES provides structure utilization monitoring which can be valuable for log streams defined to use CF structures. The FULLTHRESHOLD parameter for a CF structure specification in the CFRM policy can be used to provide consumption warnings via z/OS XES messages (that is IXC585E and IXC586I). Message IXC360I also contains significant CF structure use and consumption information for a DISPLAY XCF,STR,STRNAME=structurename command. For more information, see Monitoring structure utilization. Note: These settings are critical in cases where the log stream and
related resources may be configured to try to avoid physically moving
log data during the offload process - that is, the offload would only
delete data from interim storage and not move it to DASD. This configuration
is an approach to avoiding the most common offload inhibitors which
involve the obtaining of DASD resources. For more information on this
configuration, see Managing log data in interim storage to minimize movement to DASD
When interim storage consumption reaches a critical point, look
for indications that offload processing is not running in a normal
manner:
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