RSU

RSU=xxxx

RSU={xxxx       }
    {OFFLINE    }
    {xx%        }
    {xxxxxxM    }
    {xxxxxxG    }
    {xxxxxxT    }

This parameter specifies the amount of central storage to be made available for storage reconfiguration. The frames in these storage increments are not to be used for long-term pages and will be designated the non-preferred area. (Long-term pages include SQA pages, common area fixed pages and LSQA or private area fixed pages associated with non-swappable address spaces.)

An address space is non-swappable:

If the program name is in the program properties table (PPT) and the appropriate flags are set. (For more information about the PPT, see SCHEDxx (PPT, master trace table, and abend codes for automatic restart).)
If ADDRSPC=REAL is specified on the JOB or EXEC statement.
If the address space issues the TRANSWAP sysevent. The DONTSWAP and HOLD sysevents also make an address space non-swappable, but these specifications are considered to be of short duration, and associated LSQA and private area pages are not necessarily put into preferred storage.

During IPL, MVS™ assigns the V=R area to the low end of storage and assigns the current SQA to the high end of storage. Then, to satisfy an RSU specification, the system can define reconfigurable storage increments, starting with the first offline storage increment at the low end of storage and proceeding upward. If the system cannot satisfy the request from offline storage, it proceeds to define reconfigurable storage increments with the online storage increments. The system starts with the first online storage increment at the high end of storage and proceeds downward, defining reconfigurable storage increments using only those online storage increments that do not contain V=R, SQA, LSQA, or nucleus frames.

After the system has defined the reconfigurable storage increments, it defines the remainder of the processor storage increments as the preferred area for long-term pages.

Value Ranges:

0

If your processor complex is not using PR/SM™, or if your processor complex is using PR/SM but you are not using dynamic storage reconfiguration, set the RSU parameter to 0 (the default).

Values from 1–9999 are supported, but it is recommended that you either use the megabyte, gigabyte, or terabyte format described below, or use RSU=OFFLINE.

If you specify a value of 1-9999 without a qualifier (M, G, T, or %), the value is considered to be the number of the units, and the default storage increment size is used. For example, if your machine has a storage increment size of 64 megabytes, specifying 20 causes 20 units of 64M (1.25G in total) to be set aside for storage reconfiguration. Note that the storage increment size is entirely hardware dependent, based not only on the hardware model, but possibly also on the amount of real storage installed on the physical machine (not the LPAR). This means using an unqualified value of 1-9999 can have unexpected results, because its meaning can change dramatically with a simple upgrade to the amount of real storage on the system.

xxxxxxM

Specifies the RSU value in megabytes of storage. You can specify a six-digit value in z/Architecture® mode. The value you specify might be rounded up. See PR/SM Planning Guide for specific information.

xxxxxxG

Specifies the RSU value in gigabytes of storage. You can specify a six-digit value in z/Architecture mode. The value you specify might be rounded up. See PR/SM Planning Guide for specific information.

xxxxxxT

Specifies the RSU value in terabytes of storage. You can specify a six-digit value in z/Architecture mode. The value you specify might be rounded up. See PR/SM Planning Guide for specific information.

OFFLINE

Indicates that all of the offline storage increments are to be made reconfigurable.

xx%

Indicates that the RSU is specified as a percentage of all storage, both online and offline. The actual number of storage increments that become reconfigurable will be rounded up to a whole number of storage increments.

Note:

An uncorrectable storage error might prevent you from reconfiguring the processor. If this happens, specify an additional storage increment (on the RSU parameter), at the next IPL, to increase the chance that reconfiguration might work.
In order to eliminate the impact of transition swaps, set REAL=0 and RSU=0 if you have no requirement for reconfiguring storage and no need to run a V=R job.

If you specify an RSU value that the system cannot fully satisfy, the system defines as many reconfigurable storage increments as possible and issues message IAR004I to indicate that the RSU parameter was not completely satisfied. The operator can then issue the display matrix (D M) command to determine how many increments were made available for reconfiguration.

However, if you specify an RSU value that is greater than the total amount of real storage available on the system, message IAR026I is issued by the system during IPL indicating an RSU over-specification condition and showing the amount of real storage available on the system. This message is followed by an IAR006A message prompting for a valid RSU value. You must select the right RSU value for the system. A large RSU value can ultimately cause system performance problems and degradation.

For information about how to choose the correct RSU value, see RSU Parameter Specification section and Specifying the RSU parameter section in z/OS MVS System Commands.

Syntax Examples for the RSU Parameter:

Example 1: RSU=0. Indicates that you are not using PR/SM, or that you are not using dynamic storage reconfiguration.

Example 2: RSU=25%. This example requests that 25 percent of all storage, including online and offline, be made available for storage reconfiguration.

Example 3: RSU=300M. This example requests that 300 megabytes of storage be made available for storage reconfiguration.

Default Value: 0. If the RSU parameter is omitted or specified as 0, all processor storage increments are available for preferred storage.

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