Using the SMS enhancements

In z/OS V2R2, SMS introduces these enhancements.

SMS Space Constraint Relief

SMS space constraint relief processing provides relief for space-related failures for SMS managed data sets. When space constraint relief is requested, SMS retries an allocation that was unsuccessful due to space constraints on the volumes. Depending on the allocation characteristics, SMS may retry with a one-step or two-step process after the initial phase failed for insufficient space.

In the one-step process, SMS retries the allocation after reducing the requested space quantity based on the Reduce Space Up to (%) attribute. SMS simultaneously removes the 5-extent limit so that SMS can use as many extents as the data set allows. The one-step process is used when allocating a data set that has a volume count of 1, allocating a data set with guaranteed space or extending an existing data set to a new volume.

In the two-step process, SMS first uses a best-fit volume selection method to spread the primary quantity over multiple volumes, up to the volume count, if needed. If this fails due to space constraints, SMS continues with the best-fit method after reducing the primary quantity and removing the 5-extent limit. The two-step process is generally used when the volume count is greater than 1.

z/OS V2R2 provides the following enhancements to SMS space constraint relief:

Supports a new parameter in the data class that indicates whether space reduction on guaranteed space allocation is permitted or not.
Supports the space reduction function on non-striped guaranteed space allocations when allocating a new data set or extending an existing data set to a new volume. This space reduction function will remain unsupported for striping allocation as the system requires all stripes to have the same space quantity.
Allocates the largest possible space that satisfies the percentage specified in the parameter, Reduce Space Up to (%), during space reduction processing for both guaranteed space and non-guaranteed space allocation requests. If the reduced space is not available on the current volume, the secondary extent is allocated on another volume. For VSAM each extent must return space in multiples of the CA size. If the reduced minimum secondary allocation amount falls below the minimum CA size, then the minimum CA size is used as the minimum secondary allocation amount.
Issues a new SMS message to the job log and hardcopy log when the Dynamic Volume Count (DVC) function is invoked.

For more information, refer to the topic about Specifying attributes to handle space constraints in z/OS DFSMSdfp Storage Administration.

SMS RAS enhancements

SMS provides support for the following RAS items:

SMS issues a RESERVE with the resource name, IGDCDSXS, to serialize the access to SMS control data sets, ACDS and COMMDS. It is recommended that the SMS resource name, IGDCDSXS, be placed in the GRS RESERVE conversion RNL as a generic entry so it can be converted to the global ENQ. The purpose is to minimize delays due to contention for resources and prevent potential deadlocks. In V2R2, SMS will issue a new informational message, IGD06041I, to the console if IGDCDSXS is not specified in the GRS RESERVE conversion RNL for the system that is to participate in a global resource serialization complex.
In V2R2, SMS issues IGD030I messages indicating a syntax error when parameters, SELECT and DESELECT, specified in the SMS PARMLIB member extended to a third line. For example:
SELECT(ACSINT,ACSPRO,
VTOCA,VTOCC,
IDAX,CATG,MSG,MODULE) <-- Error on the third line
This item is to remove the restriction and allow these SMS PARMLIB parameters to extend beyond the second line.
ACS messages IGD01012I and IGD01015I are enhanced to include the data set name and the storage group name for problem diagnosis. SMS trace entries that are related to these events are also enhanced.
Prior to V2R2, SMS issued message IGD17800I when the specified volume(s) for a guaranteed space request or the volume provided by AMS for an AIX define can not be found in the eligible storage group list. The storage group(s) searched by SMS is not externalized to the user. To improve problem diagnosis, message IGD17800I is enhanced to display the storage group(s) that are searched.
The RETENTION LIMIT value in the Management Class limits the use of retention period and expiration date. Data sets that are assigned with a RETENTION LIMIT value of zero days specified in their Management Class are immediately expired with an IGD17364I message issued to the job log. This has caught some users by surprise, and they needed to recover these data sets. To facilitate this task, this item will also externalize IGD17364I to the hardcopy log. This allows the user to identify these expired data sets by searching for the IGD17364I messages in the hardcopy log. Prior to V2R2, the user may need to go through the joblogs to identify these data sets.

User-defined ACS read-only variable

SMS provides the ability to specify user-defined values for use with ACS routines. You use a new parameter in the IGDSMSxx member of PARMLIB, as follows: USER_ACSVAR(value1,value2,value3). The values for USER_ACSVAR are saved when SMS is started and, during ACS processing, are passed to the ACS routines in the form of a new ACS read-only variable, &USER_ACSVAR. You can alter the values with the SETSMS command.

For details, refer to the following topics:

For information about ACS routines, refer to ACS routines in z/OS DFSMSdfp Storage Administration.
For details on the IGDSMSxx member of PARMLIB, refer to IGDSMSxx in z/OS MVS Initialization and Tuning Reference.
For details on the SETSMS command, refer to SETSMS in z/OS MVS System Commands.

Storage group space alert messages

SMS provides new alert thresholds for pool storage groups. You can define the thresholds with these attributes:

Total Space Alert Threshold %
Track-Managed Space Alert Threshold %

For more information about the attributes, refer to the topic about Values for defining a pool storage group in z/OS DFSMSdfp Storage Administration.

New alert messages are issued to the console when the alert thresholds have been reached:

IGD400I, for total space
IGD401I, for track-managed space

SMS calculates the space usage of a pool storage group when a space change occurs on an online and enabled volume in the pool storage group or when an enabled volume in the pool storage group is varied online or offline.

A new keyword, ALERT, is added to the DISPLAY SMS command, to display all of the storage groups that have reached one of their alert thresholds. You can use DISPLAY SMS,STORGRP(ALERT) or DISPLAY SMS,STORGRP(ALERT),LISTVOL. When no storage groups have reached the threshold, a new version of message IGD004I is issued.

In addition, the IGD002I messages issued for DFSMS DISPLAY SMS,STORGRP commands include new information about total and track-managed space for each storage group.

For details about the messages, refer to z/OS MVS System Messages, Vol 8 (IEF-IGD)