# Logical Control Unit

The Logical Control Unit attributes provide performance information for a logical control unit.

All Channels Busy Percent: The percentage of the time all channel paths to this LCU were busy.

Attached Channels: The total number of channel paths that have defined connections to the LCU.

Average Delay Queue: The average number of delayed requests on the control unit header (CU-HDR). This field is calculated as the accumulated Q length minus the number of enqueued requests divided by the number of enqueued requests.

Channel Path I/O Rate: The Channel Path I/O rate for I/Os to this LCU. This field is calculated as the number of I/O operations accepted on this channel path divided by (sample time minus interval start time).

Contention Rate: The rate per second at which the SAP places delayed I/O requests on the CU-HDR for this LCU. This is done when all paths to the subchannel are busy and at least one path to the control unit is busy.

Control Unit Busy Percent: The percentage of requests deferred due to control unit busy.

DCM Channels Attached: The flag indicating that there are DCM channels attached to this LCU.

DCM Channels Channel Path I/O Rate: The Channel Path I/O rate for I/Os to this LCU. This field is computed as the number of I/O operations accepted on this channel path divided by (sample time minus interval start time).

DCM Channels Control Unit Busy Percent: Shows the relationship for each channel path of the LCU, between requests deferred due to control unit busy and total successful requests serviced by that path. Each CHPID of the LCU measures the distribution of control unit contention. This number is derived from: the number of deferred I/O requests due to control unit busy divided by the following combined values:

- (the number of deferred I/O requests due to director port busy +
- the number of deferred I/O requests due to control unit busy +
- the number of successful I/O requests on that path) * 100

DCM Channels Defined: The number of DCM channels defined for this LCU.

DCM Channels Director Port Busy Percent: Indicates director port contention. This value represents the number of times an I/O request was deferred because the director port was busy during the measurement interval. This value is derived from the number of deferred I/O requests due to director port busy divided by the following combined values:

- (the number of deferred I/O requests due to director port busy +
- the number of deferred I/O requests due to control unit busy +
- the number of successful I/O requests on that path) * 100

DCM Channels Maximum: The maximum number of DCM channels used for this LCU.

DCM Channels Minimum: The minimum number of DCM channels used for this LCU.

Director Port Busy Percent: The percentage the director port is busy. This field indicates director port contention. This value is the number of times an I/O request was deferred because the director port was busy during the measurement interval.

High DFW Retry Percent: The highest DFW retry percentage of any volume on this LCU.

High Volume MSR: The highest MSR (millisecond response time) of any volume on this LCU.

High Volume Utilization: The highest percentage busy of any volume on this LCU.

I/O Per Second: The channel Path I/O Rate for I/Os to this.

LCU Hex Number: The character representation to the hexadecimal number of this LCU.

LCU Number: The HCD-assigned number for this logical control unit. An LCU is a logical representation of either a single control unit, with or without attached devices, or a group of control units that share devices.

Low Read Hit Percent: The lowest read hit percentage of any volume on this LCU.

Low Write Hit Percent: The lowest write hit percentage of any volume on this LCU.

Managed System: The SMS name of this system.

Maximum HyperPAV Unavailable Alias Percent: The maximum percent of the number of I/Os that could not start for a control unit because a HyperPAV alias was not available.

Maximum I/Os Queued: The maximum number of I/Os queued for a control unit.

NonSMS Volumes: The total number of nonSMS-managed volumes on this LCU.

PDS Record: A single record of trend data retrieved from persistent data store.

SMS Volumes: The total number of SMS-managed volumes on this LCU.

Time Stamp: The date and time associated with this row.

Total Volumes: The count of the total number of volumes in this LCU.