Displaying ring status

The DISPLAY GRS (D GRS) command shows the state of each system in the complex and the status of the links that connect the systems. Note that D GRS shows system status only as it relates to the global resource serialization ring. D GRS does not reflect how well a system is running generally; for example, MVS™ on a system shown as QUIESCED or INACTIVE in the global resource serialization complex might run successfully for quite a while.

You can also use D GRS to display the local and global resources requested by the systems in the ring, contention information, or the contents of the RNLs. These uses are described in z/OS MVS System Commands.

You can issue D GRS from any system in the ring and at any time after the ring has been started. The D GRS display shows the status of the ring from that system's point of view; thus, the displays issued from different systems might show different results. Figure 1 shows an example of the information D GRS produces and explains the values that can appear in each field.

D GRS is most useful, however, when a ring failure has occurred. The information displayed can help the operator to make informed decisions about the cause of an error and the correct response to the problem. Note that D GRS does not diagnose a problem; it simply reports status. Figure 2 shows how an operator can use D GRS to determine the cause of a problem with ring processing.

Figure 1. D GRS Explanation (Mixed Complex)

18.40.07  ISG343I  18:40:06  GRS STATUS 340
SYSTEM    STATE       COMM    SYSTEM    STATE      COMM
SYS2      ACTIVE              SYS1      ACTIVE     YES
SYS3      QUIESCED    YES     SYS4      QUIESCED   NO

LINK      STATUS      TARGET  LINK      STATUS     TARGET
 220       ALTERNATE   SYS3    420      ALTERNATE   SYS3
 221       ALTERNATE   SYS3    421      ALTERNATE   SYS3
 224       QUIET       SYS4    424      QUIET       SYS4
 225       QUIET       SYS4    425      QUIET       SYS4
 228       ALTERNATE   SYS1    428      ALTERNATE   SYS1
 229       IN-USE      SYS1    429      ALTERNATE   SYS1

SYSTEM

The name of the system.

STATE

The state of the system at the time when the command was issued. There are seven possible states:

ACTIVE: The system is part of the ring and is actively participating in global resource serialization. ACTIVE is the normal condition. The system accepts all commands related to ring processing.
QUIESCED: The system is temporarily suspended from the ring, in response to either a ring disruption or operator command. The system does not have current information about global resources and is not currently processing global resource requests. Users of global resources retain ownership, but any users who try to obtain or free a global resource are suspended. The system remains quiesced, and the users remain suspended, until the system is restarted. Note: Access to local resources is not affected, but an attempt to cancel a job might not succeed if a global resource is involved.
INACTIVE: The system is not part of the ring. INACTIVE appears when a ring disruption has occurred. The system has current information about global resources but is not currently processing global resource requests. Users of global resources retain ownership, but any users who try to obtain or release a global resource are suspended. Multiple systems can be INACTIVE, and an inactive system can restart the ring. An inactive system remains inactive until any system in the complex is restarted. Note: Access to local resources is not affected, but an attempt to cancel a job might not succeed if a global resource is involved.
JOINING: The system is joining the ring as part of its IPL process.
RESTARTING: The system is re-entering the ring as a result of a RESTART command.
ACTIVE+VARY: The system is executing a VARY GRS command.
ACTIVE+WAIT: A VARY GRS command was issued, but it is waiting because another VARY GRS command is now executing. When ACTIVE+WAIT appears, another system normally shows ACTIVE+VARY.

COMM

An indication of whether or not the system has responded to a request for status. YES indicates that the system shown can communicate with the system issuing D GRS. NO indicates that there is no communication link, the system is temporarily stopped, or the system has failed. If NO appears, the state shown for the system might not be accurate. The field is blank for the system that issued D GRS.

LINK

The address of each CTC data link defined for global resource serialization on the system.

STATUS

The status of the link. There are four possible states:

IN-USE: The link is a primary link now being used to send the RSA-message from one system to another. IN-USE appears only for a link that connects active systems.
ALTERNATE: The link is an alternate. If a primary link fails, an alternate link can automatically replace it. An alternate link might be used to send the ring acceleration signal, which D GRS does not report; if an alternate link used for ring acceleration replaces a failed primary link, it can no longer send the ring acceleration signal.
DISABLED: The link is not physically connected or was taken offline because of an error.
QUIET: The link does not have any apparent problems, but the system it connects to did not respond to the request for status.

TARGET

The name of the system that last responded from the other side of the link. The field is blank when the link has been disabled since the IPL of the system or when the system did not respond to the request for status.

Figure 2. Using D GRS to Analyze a Problem

18.40.07  ISG020I  18:40:06  GRS STATUS 340
SYSTEM    STATE       COMM    SYSTEM    STATE      COMM
 SYS2      ACTIVE              SYS1      ACTIVE     YES
 SYS3      QUIESCED    YES     SYS4      QUIESCED   NO

LINK      STATUS      TARGET  LINK      STATUS     TARGET
 220       ALTERNATE   SYS3    420      ALTERNATE   SYS3
 221       ALTERNATE   SYS3    421      ALTERNATE   SYS3
 224       QUIET       SYS4    424      QUIET       SYS4
 225       QUIET       SYS4    425      QUIET       SYS4
 228       ALTERNATE   SYS1    428      ALTERNATE   SYS1
 229       IN-USE      SYS1    429      ALTERNATE   SYS1

The COMM field for system SYS2 is blank; the D GRS command was issued on system SYS2. The display shows the following:

System SYS2 and system SYS1 are active; they are processing global resource requests.
System SYS2 and system SYS1 are using link 229 to send the RSA-message. Link 229 is a primary link; its status is IN-USE.
All other links between system SYS2 and system SYS1 (228, 428, 429) are shown as ALTERNATE. One of these links might be sending the ring acceleration shoulder-tap.
The status of system SYS3 is QUIESCED. It is not part of the ring and is not processing global resource requests. YES appears in the COMM field for system SYS3, indicating that system SYS3 responded to the request for status. MVS is still active on system SYS3.
Because system SYS3 is quiesced, all of its links to system SYS2 (220, 221, 420, 421) are marked as ALTERNATE.
The status of system SYS4 is QUIESCED. Like system SYS3, it is not part of the ring and is not processing global resource requests. NO appears in the COMM field for system SYS4, indicating that system SYS4 (unlike system SYS3) did not respond to the request for status. Also, all links between system SYS4 and system SYS2 (224, 225, 424, 425) are marked as QUIET. System SYS4 is the source of the problem.
D GRS can report a problem but it cannot diagnose the reason for the problem. Possible reasons for the problem shown in this example are:
1. System SYS4 is temporarily stopped. Perhaps the system has stopped to take a dump, or MVS might be in a spin loop.
2. System SYS4 has failed.
3. All links have failed on the system SYS4 side. This possibility is unlikely; an I/O error on a link is normally detected by both systems (SYS2 and SYS4 in this case), and the status of a failed link normally appears as DISABLED.