US 5,471,631 AGranted

Using time stamps to correlate data processing event times in connected data processing units

AssigneeInternational Business Machines Corporation

InventorsBrent C. Beardsley, Allen C. Brailey, Peter L. H. Leung

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Abstract

A host processor(s) is loosely-coupled by a plurality of data channels to a peripheral subsystem(s). The host processor(s) has a time of day clock. The peripheral subsystem(s) has a cluster(s) that performs peripheral controller functions. Each cluster has first and second clocks that respectively generate a log entry (logging) reference time and a subsystem time. The first and second clock times result in subsystem time stamps in a log that are not related to the time of day clock. For time correlating the time of day clock with the first and second clocks, a host time stamp is generated from the time of day clock. The host time stamp is sent to the subsystem via one of the data channels for entry into the log with the current time stamps of the first and second clocks as a time-correlating entry. Queue delays in the host processor accessing a data channel for sending the host time stamp and in the subsystem for recording the time-correlating entry are compensated for by updating the host time stamp and by generating an entered time stamp at the time of recording the time-correlating entry. Time stamp correlating operations by a host processor enable recovery from a lost host time stamp.

Claims46

Dependent claims

A data processing (DP) system having two DP means, said two DP means comprising host processor DP means and peripheral subsystem DP means, data channel means connecting the host processor DP means to the peripheral subsystem DP means for exchanging control information and data therebetween, said host processor DP means having a time of day clock, a data storage means in the peripheral subsystem DP means;

the improvement including, in combination:
a peripheral time clock in the peripheral subsystem DP means that continuously operates for indicating a peripheral time in the peripheral subsystem DP means;
time stamping means in the peripheral subsystem DP means connected to the peripheral time clock for reading said peripheral time for storing in said data storage means said read peripheral time as a logging time stamp;
a first one of said DP means, via said data channel means, sending a correlation request to a second one of said DP means, said host processor DP means is to send, via said data channel means, a current time of said current time of say indication to said time stamping means, said host processor DP means responding to said correlation request to read said current time of day indication and then send said read current time of delay indication as a host time stamp to said peripheral subsystem DP means via said data channel means;
said time stamping means being connected to said data channel means for receiving said host time stamp, said time stamping means connected to said peripheral time clock, said time stamping means responding to receiving said host time stamp to read a current time of said peripheral time clock for generating a time-event logging time stamp and recording both said host time correlating entry in said data storage means;
and
data processing event means connected to said data storage means and to said time stamping means for recording in said data storage means a second read time of said peripheral time clock as a predetermined logging time stamp plus data indicating a predetermined data processing event.

4 more elements

A method of operating a data processing (DP) system having host processor DP means and peripheral subsystem DP means, data channel means connecting the host processor DP means to the peripheral subsystem DP means for exchanging control information and data between said DP means, said host processor DP means having a time of day clock indicating a current time of day, data storage means in the peripheral subsystem DP means;

the method including steps of:
continuously generating a first peripheral time for indicating time in the peripheral subsystem DP means;
reading said current time of day indication from said time of day clock and sending said read current time of day indication to said peripheral subsystem DP means as a host time stamp;
upon receipt in said peripheral subsystem DP means of said host time stamp, reading said first peripheral time, making said first peripheral time a logging time stamp, then inserting said received host time stamp and said logging time stamp into a time-correlating entry and storing the time-correlating entry in said data storage means;
and
detecting and indicating a predetermined data processing event in the peripheral subsystem DP means, in response to said indicated predetermined data processing event, reading said first peripheral time for generating a second logging time stamp, generating an event log entry including said second logging time stamp and said indicated predetermined data processing event and storing the event log entry in said data storage means.

3 more elements

In a peripheral subsystem, a data-storage cluster having storage path means, a data channel adaptor connected to the storage path means, a device adapter means connected to the storage path means such that the storage path means provides for data transfers between said data channel adaptor and said device adapter means, data storage means connected to the storage path means, support facility means connected to the data storage means and to the storage path means, the improvement, including, in combination:

first clock means in the support facility means for generating and indicating a first time in a first time granularity;
second clock means connected to the support facility means and to the storage path means for generating and indicating a second time in a second time granularity;
LOG means in the data storage means for storing a plurality of event and time-correlating entries;
time stamp means in the support facility means connected to the data channel adaptor for receiving a host time stamp from the channel adaptor, connected to the first and second clock means for receiving the first and second time indications and combining said host time stamp, said first time indication and
said second time indication into a time-correlating entry and storing the time-correlating entry in said LOG means;
event recording means connected to said LOG means and to the first clock means and having event indicating means for indicating a predetermined event occurring in the peripheral subsystem, said event recording means combining said indicated event, said first time indication for generating an event log entry and for recording said event log entry in said LOG means;
and
data processing event means connected to event indicating means for sending an indication of a predetermined data processing event for recording in said LOG means, said event indicating means being responsive to receiving said indication of said predetermined data processing event to indicate said predetermined event.

5 more elements

A method of operating a peripheral subsystem, said peripheral subsystem having a data-storage cluster having storage path means, a data channel adaptor connected to the storage path means, a device adapter means connected to the storage path means such that the storage path means provides for data transfers between the connected adapters, data storage means connected to the storage path means, support facility means connected to the data storage means and to the storage path means;

the method including steps of:
generating and indicating, in said support facility means, a first time indication in a first time granularity;
generating and indicating a second time indication in a second time granularity;
establishing a LOG means in the data storage means;
receiving from said data channel adaptor a host time stamp;
receiving the first and second time indications and combining said first and second time indications with said host time stamp for creating a time-correlating entry, then storing the time-correlating entry in said LOG means;
detecting and indicating a predetermined data processing event;
recording in said LOG means said predetermined data processing event and said first time indication as a log entry.

5 more elements

Dependencies are inferred from the claim text.