If z/VM is not sending reserve and release CCWs to your devices, take extra steps to make z/VM send these CCWs to your devices. This ensures that access is serialized among real processors. To make z/VM forward reserve CCWs temporarily (that is, until the next time you perform an IPL), issue a SET SHARED command for that device. Specify the device address as a parameter on the command. For example, to make z/VM send reserve CCWs to device 123, issue this Class B command:
SET SHARED ON FOR 123
To make z/VM forward reserve CCWs permanently, specify SHARED=YES on the RDEVICE macro in the HCPRIO assembly file or SHARE YES on the RDEVICE macro in the system configuration file. Repeat this step for each shared device. Your changes to the RDEVICE macro take effect the next time you perform a system generation and IPL for z/VM.
Be certain your control file is defined as a full pack minidisk if you want to send real reserve/release orders to the hardware. z/VM suppresses reserve release orders, even if you set SHARED ON, if the minidisk is not a full pack.
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