Monitoring Available ASP Storage

Until OS/400 V4R2, the ASP storage threshold was the only tool that administrators had for monitoring disk usage. With V4R2, IBM added the following two system values that also monitor disk usage.
1. The auxiliary storage lower limit system value (QSTGLOWLMT), which, in contrast to the ASP storage threshold, specifies how low your available storage capacity can go before the system takes action. Available storage capacity is defined as the percentage of free ASP storage space. This means that this system value, and its companion value, QSTGLOWACN, focus on how much storage is still available on your machine, rather than on how much storage is already used. To set up your system properly, your QSTRGLOWLMT value should meet the following relationship:
QSTGLOWLMT <= (100 - Storage Threshold)
i5/OS does not monitor to insure that QSTGLOWLMT satisfies this relationship, but it's important to note that your ASP storage threshold monitoring will never be activated if this equation is reversed and QSTGLOWLMT is greater than 100 less the storage threshold.
New i5 systems are shipped with a default QSTGLOWLMT value of 5 percent.

2. The auxiliary storage lower limit system value (QSTGLOWACN), which specifies what action will be taken when available storage capacity falls below the percentage listed in the QSTGLOWLMT system value. You can set QSTGLOWACN to one of the following values:
*MSG: This option sends a CPI099C message (Critical storage lower limit reached) to the QSYSOPR message queue when your available storage percentage falls below QSTGLOWLMT. It's also worth noting that the system will also send CPI099C messages to QSYSOPR when QSTGLOWLMT is set to any other value. By default, QSTGLOWACN is set to *MSG for new i5 systems.
*CRITMSG: This option sends message CPI099B (Critical storage condition exists) as a break message to any user or class of users that are defined in the Critical messages to user parameter (CRITMSGUSR) in your partition's service attributes