Uninterruptible power supply delay time system value (QUPSDLYTIM)

The uninterruptible power supply delay timer (QUPSDLYTIM) controls the length of time that the system waits before saving main storage and powering down the system.

If utility power is restored before the wait time ends, the system resets the timer. If the wait time is exceeded, the system begins to save main storage and goes into a controlled shutdown.

The time that is specified by the QUPSDLYTIM system might be one of the following values:

If you set QUPSDLYTIM to *NOMAX, the following conditions must be met or the system begins an immediate shut down:

Figure 1. QUPSDLYTIM values and actions

Notes:

The default value for QUPSDLYTIM is *CALC. Leaving QUPSDLYTIM set to *CALC may defeat the purpose of having an uninterruptible power supply. *BASIC and *CALC provide the same function in systems that are running V3R6 or later releases of the operating system.
If QUPSDLYTIM is set to *BASIC or *CALC, the system will perform a controlled shutdown after a fixed interval delay of 200 seconds. If you have an uninterruptible power supply, you can specify a numeric value.

The flow chart shows the values and actions of the QUPSDLYTIM system values. The flow chart starts with three boxes across the top of the chart.

The first box on the top is labeled "Utility failure and No uninterruptible power supplyor UPS failure." Two arrows proceed from this box. One arrow points to a box labeled "Internal battery."

The other arrow points to a box labeled "No internal battery." The box that is labeled "Internal battery points to another box labeled "30 second delay." The box that is labeled "30 second delay" points to a box that is labeled "90 second shutdown."

The box that is labeled "No internal battery" points to a box that is labeled "Uncontrolled shutdown."

The second box on the top is labeled "Utility failure and uninterruptible power supplyoperating correctly." An arrow from this box points to another box that is labeled "QUPSDLYTIM SETTING." This box shows the three settings for the QUPSDLYTIM setting, which are *NOMAX, numeric value, and *CALC or *BASIC.

If *NOMAX is selected, an arrow points to another box that is labeled "Return." If numeric value is selected, an arrow from the QUPSDLYTIM SETTING box points to another box that is labeled "User defined delay." Another arrow from the "User defined delay box points to a box that is labeled "Shutdown." If *CALC or *BASIC is selected, an arrow from the QUPSDLYTIM SETTING box points to another box that is labeled "200 second delay." The 200 second delay box points to the box that is labeled "Shutdown."

The third box is labeled "Utility failure and uninterruptible power supplybattery low." This box points to the box that is labeled "Shutdown."

Determining the value of QUPSDLYTIM

To determine the value of QUPSDLYTIM, you need to know the following information:

The hold-up time of your uninterruptible power supply at the given load (the battery-rated time).
The amount of time it takes your system to save main storage and turn off.

Available battery run time

The available battery run time is a dynamic variable. Evaluate your system's available battery with these questions:

Has the power been fluctuating?
Has the battery been previously discharged?
Is the battery fully charged?

The actual battery run time is a function of capacity. Even if the battery is fully charged, it might not have 100% capacity. A typical battery will lose 20% to 50% of its rated capacity in 4 to 5 years, depending on ambient room temperatures. Elevated operating temperatures tend to increase the loss of capacity. The actual battery run time is also a function of the discharge load. The more loads the uninterruptible power supply serves, the less time it can sustain them. When the battery on the system falls below a specific level of charge, the uninterruptible power supply issues a weak battery condition signal. The weak battery condition signal from uninterruptible power supply affects the shutdown mechanisms.

The time it takes to save main storage and power-down is not an exact number. Save time depends on the number of changes in main storage that have not been written to disk. The number of disk arms available is also a factor; the more disk arms, the faster the system can write main storage to disk. The system power-down will also depend on the number of jobs and the average amount of time it takes to end them. Typically a job will be close to an instruction boundary; however, some instructions are long running. The following formula shows a worst case scenario in estimating the number of minutes it will take to shut down a system:

 ((0.0554*(MS size in MB))/(# of disk arms)) + 1.6 = # of minutes

Refer to the following table for an estimate of the time required to write main storage to disk on your particular system. The amount of time required to shut down a system typically is a small percentage of this value.

Table 1. Time needed in minutes to write main storage to disk
Arms	32MB	64MB	128MB	256MB	512MB	1GB	2GB	4GB	8GB	16GB	32GB	64GB	128GB
2	2.5	3.4	5.1	8.7	15.8	30.0	58.4	115.1	228.7
4	2.0	2.5	3.4	5.1	8.7	15.8	30.0	58.4	115.1	228.7
8	1.8	2.0	2.5	3.4	5.1	8.7	15.8	30.0	58.4	115.1	228.7
16	1.7	1.8	2.0	2.5	3.4	5.1	8.7	15.8	30.0	58.4	115.1	228.7
32	1.6	1.7	1.8	2.0	2.5	3.4	5.1	8.7	15.8	30.0	58.4	115.1	228.7
64		1.6	1.7	1.8	2.0	2.5	3.4	5.1	8.7	15.8	30.0	58.4	115.1
128			1.6	1.7	1.8	2.0	2.5	3.4	5.1	8.7	15.8	30.0	58.4
256				1.6	1.7	1.8	2.0	2.5	3.4	5.1	8.7	15.8	30.0
512					1.6	1.7	1.8	2.0	2.5	3.4	5.1	8.7	15.8
1024						1.6	1.7	1.8	2.0	2.5	3.4	5.1	8.7
Assumes all pages in main storage have been modified and changes have not yet been written to disk. Proportionately less time is required if fewer pages need to be written to disk.

Parent topic:

Controlled shutdown concepts