z/OS memory objects report


Strobe produces the z/OS Memory Objects report when it encounters z/OS memory objects. It identifies memory objects created by an application that are present when measurement takes place. The first section of the report, entitled MEMORY OBJECTS - FIRST OBSERVATION, lists the memory objects Strobe first detects during measurement, The last section of the report, entitled MEMORY OBJECTS - LAST OBSERVATION, lists the memory objects Strobe detects during its last measurement observation. If Strobe detects an observation where the sum of usable bytes exceeds the first and last observations, it lists data for these memory sections in the section entitled MEMORY OBJECTS - HIGHEST OBSERVATION OF USABLE BYTES.

z/OS Memory Objects Report

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MEMLIMIT

The maximum amount of storage the address space can obtain above the bar, in megabytes.

SOURCE

Indicator of how MEMLIMIT was set:


    • SMF - value set by SMFPRMxx member in the MVS parmlib, by SETSMF, or by SET SMF commands
    • JCL - value set by JCL region parameter
    • Region=0 in the JCL
    • IEFUSI installation exit
    • Unix OMVS
    • Unix SETRLIMIT
    • Unix SPAWN
    • Unix SETOMVS
    • Authorized Application.

ORIGIN ADDRESS

Origin address of the memory object in megabytes. (If guard bytes are in the front of the memory object, the start address would be the guard bytes added to the origin address of the memory object. If guard bytes are high, the origin address and start address are the same.) If guard bytes are mixed, Strobe cannot determine the start address.

USER/CREATOR

CSECT module name of the memory object user.


    • A prefix of C- indicates the user is the owner and creator of the memory object.
    • A prefix of S- indicates the user is the owner and creator of the shared memory object.
    • A prefix of U- means the user is working with a shared memory object.

HEX OFFSET

The offset in the module (requestor or module name) that requested the IARV64 GET function. If the module name is .UNKNOWN, the offset will be the address in the PSW.

CRE ASID

ASID of the creator of the memory object.

STATUS/USER TOKEN

Indicator of the control authority required for certain services:


    • A - If the last four bytes of the user token are binary zeros, only authorized callers can free a memory object. The memory object is eligible for PAGEFIX and PAGEUNFIX by authorized callers. Memory objects with a status of authorized can only be created by authorized callers. An authorized caller is one that is in supervisor state or has a storage key of 0 to 7.
    • U - If the memory object may be freed by an unauthorized caller that owns the memory object, then the first four bytes of User Token are binary zeros and a U appears under status. The memory object is not eligible for PAGEFIX and may only be deleted by the unauthorized caller that created the memory object. Unauthorized callers are those in problem state with storage key of 8 or greater.

USER TOKEN is the token specified by the user to be associated with this memory object. If guard bytes are low, the last four bytes of the user token are binary zeros. If guard bytes are high or not in use, the first four bytes of user token are zero. The actual user token is four bytes and can be any hexadecimal value, except binary zeros. If the user token consists of four displayable characters, they will be displayed; otherwise they will be displayed in hexadecimal format.

SPK/PROT

The storage protection key was specified when the memory object was created:


    • -N suffix indicates that the memory object is not read protected.
    • -Y suffix indicates the memory object is read protected.

SD

The SVC dump option. Y indicates the memory object is to be included if an SVC dump of the address space is taken. N indicates the memory object is not to be included in the SVC dump.

SIZE (MB)

The calculated size of the memory object.

Ending address is not shown, but you may calculate it by adding SIZE to ORIGIN ADDRESS and subtracting 1.

GUARD BYTES (MB)

Guard size in megabytes. Guard bytes is a value returned by the IARV64 macro for each memory object. The value may be followed by a letter indicating the location of the guard bytes:


    • L - guard bytes are low (precede the usable area)
    • H - guard bytes are high (follow the usable area)
    • M - mixed mode (memory object has both high and low guard bytes).

USABLE MB

USABLE MB is calculated from the previous two fields: SIZE (MB) - GUARD BYTES (MB).

AS HIGH WATER MARK MB

The largest amount of 64-bit storage that has been allocated in the measured address space from address space creation. This value may not reflect observed values for the address space during the measurement.

NET CHANGE FROM FIRST OBSERVATION

Memory objects for the first observation encountered that contained one or more memory objects, the observation that had the most usage bytes when summing the usable bytes for all memory objects in the observation, and then the last observation that contained one or more memory objects. If either the first or last observation was also the observation with the most usable bytes, then only two observations are shown: first and last.

NET CHANGE FROM HIGHEST OBSERVATION

Net change between the observation having the most usable bytes and the last observation.

Note

High Water Mark is an observed value for each observation, while usable bytes, guard bytes, and size are the sum of the values for all memory objects in the observation. All measurements are in megabytes, and the results can be negative.

 

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