IOS_STORAGE_IOSBLKS

Description:

This check verifies that control blocks used in IOS can reside in 31-bit addressable storage.

Reason for check:

Control blocks used to initiate I/O were obtained in storage addressable in the first 16 megabytes of storage so that 24-bit AMODE legacy software could perform scans on them. However, forcing all I/O control blocks below the 16 megabyte line creates a constraint on the amount of storage below the line. IBM® recommends that the control blocks be allowed to be in 31-bit addressable storage.

You can verify the state of IOS blocks using the following console command:

DISPLAY IOS,STORAGE

In response to this command, the system issues message IOS089I to display the state of captured UCB protection:

IOS089I 12.21.54 STORAGE DATA 246                          
IOS BLOCKS RESIDE IN 31 BIT STORAGE

To change the state of the IOS blocks, see the SETIOS command in z/OS MVS System Commands.

z/OS® releases the check applies to:

z/OS V1R12 and later.

Parameters accepted:

Yes, the following parameters are accepted:

PARM(‘IOSBLKS(state)')

Since, there may be a rare instance where 31-bit IOS Blocks should not be enabled, you can set the expected state of 31-bit IOS blocks the check expects to either:

PARM('IOSBLKS(31)') which is the default, indicates that the expected state for IOS blocks is 31–bit.
PARM('IOSBLKS(24)') indicates that the expected state for IOS blocks is 24–bit.

User override of IBM values:

The following shows the default keywords for the check, which you can override on either a POLICY statement in the HZSPRMxx parmlib member or on a MODIFY command. This statement may be copied and modified to override the check defaults:

UPDATE
     CHECK(IBMIOS,IOS_STORAGE_IOSBLKS)
     INACTIVE
     SEVERITY(LOW) INTERVAL(ONETIME) DATE('date_of_the_change')
     REASON('Your reason for making the update.')

Debug support:

No.

Verbose support:

No.

Reference:

For more information, see information on the SETIOS command in z/OS MVS System Commands.

Messages:

This check issues the following exception messages:

IOSHC103E

See IOSHC messages in z/OS MVS System Messages, Vol 9 (IGF-IWM).

SECLABEL recommended for MLS users:

SYSLOW