Statements and parameters for GRSCNFxx

ACCELSYS(num)

Specifies the threshold for global resource serialization ring acceleration and the number of systems that must see a resource request before it is granted. To use ring acceleration, every system must have a link to every other system. Ring acceleration requires a fully connected complex, and it also requires an alternate link for each connection not in the sysplex. When the ACCELSYS keyword is not specified, ring acceleration is turned off. The maximum performance benefit is provided when the ACCELSYS threshold value is 2.

Specifying a different ACCELSYS value for different systems in a complex is allowed, but the complex uses the highest ACCELSYS value specified to determine when to send the shoulder-tap acknowledgment. If the highest value is greater than the number of systems in the ring, the shoulder-tap acknowledgment does not take place. To ensure that shoulder-tap processing occurs, specify ACCELSYS(num) on all systems in the ring, making sure that the value of num is less than the number of systems in the ring.

Value range: The ACCELSYS threshold value range is 2 - 99.

Default: 99

CTC(device number)

Identifies the device number of a CTC link that is attached to this system that is dedicated to the use of global resource serialization. Only one device number can be specified on each CTC parameter, but up to 64 different CTC parameters can be specified. If this system is a member of a sysplex, it is not necessary to specify the CTC parameter unless this system must have a link to a system outside of the sysplex.

Value range: 3 or 4 hexadecimal digits. The device number cannot be preceded by a slash.

Default: None

CTRACE(member-name)

Specifies the member of SYS1.PARMLIB that contains the default global resource serialization component tracing options.

Value range: The 8-character member name must be in the format CTnGRSxx, where:

n: An alphanumeric character to specify the source of the member. IBM-supplied members use I.
xx: Any two characters to identify the member.

Default: CTIGRS00

The contents of CTIGRS00 are as follows:

TRACEOPTS
      OFF
      OPTIONS('CONTROL','MONITOR')
      BUFSIZE(16M)

For more information about specifying options for the global resource serialization component trace, see z/OS MVS Diagnosis: Tools and Service Aids . For information about specifying the component trace member of SYS1.PARMLIB, see CTncccxx (component trace parameters).

GRSQ{(ALL)}

{(CONTENTION)}

{(LOCAL)}

The GRSQ keyword is only relevant for star mode. It is ignored for ring and none mode. When the SDATA=GRSQ option is specified, the GRSQ keyword collects global resource serialization information during SYSMDUMP and SVC dump processing. ENQ resource information from all systems in the global resource serialization complex is gathered and placed into the dump. This can be time consuming when running in star mode because global resource serialization needs to collect and merge information from all systems in the sysplex. The time it takes increases as more systems are added to the sysplex or the number of concurrent ENQs increase, or both. The GRSQ keyword allows the installation to limit the data collected and therefore lessen the time that is needed to complete the dump.

GRSQ(CONTENTION) causes GRSQ processing to collect all ENQ resources on the local system, and only collect information about global resources in contention in the rest of the GRS complex.
GRSQ(LOCAL) causes GRSQ processing to collect all ENQ resources on the local system only. This is not a recommended value and should only be used as a circumvention. The GQSCAN that is issued does not collect data from the other systems.
GRSQ(ALL) causes GRSQ processing to collect all ENQ resources from all systems in the entire GRS complex. Specifying GRSQ(CONTENTION) adds WAITCNT=1.

Default: CONTENTION

MATCHSYS{(name)}

{(*) }

Identifies the system that is defined in the GRSDEF statement. A system that is being initialized compares the value that is specified on the SYSNAME system parameter to the value specified for MATCHSYS to locate its GRSDEF statement in GRSCNFxx. Omitting MATCHSYS or specifying MATCHSYS(*) is regarded as a match unless a GRSDEF statement exists with an explicit name that matches the SYSNAME value. Including both a GRSDEF statement with an explicit MATCHSYS name and a GRSDEF statement with MATCHSYS(*), either explicitly or by default, thus does not cause a syntax error; the system ignores the GRSDEF statement with MATCHSYS(*).

Global resource serialization initialization processing searches the statements in GRSCNFxx until it finds a GRSDEF statement that matches the SYSNAME value, then uses the information in the statement to continue initialization. It issues an error message if it finds no match.

Value range: 1 - 8 alphanumeric characters, including the @,#, and $ characters.

Default: *

MONITOR{(YES)|(NO)}

Indicates whether the system defined in the GRSCNFxx MATCHSYS parameter is to have GRS SMF 87 monitoring activated.

Default: NO

Note: See in z/OS MVS Planning: Global Resource Serialization for more information.

REJOIN{(YES)|(NO)}: Indicates whether the system defined in the MATCHSYS parameter can automatically rejoin the active ring, after that system was stopped, then started. Specifying REJOIN(YES) eliminates the need for the operator to issue a VARY GRS, RESTART command to have the system join the active ring.
Note: If this system is a member of a sysplex, regardless of what you specify, REJOIN is set to REJOIN(YES).

Default: YES

RESMIL(number|OFF)

Specifies the RSA-message residency time.

A value, if specified, indicates the minimum RSA-message residency time in milliseconds, (that is, the least amount of time that the RSA-message is to spend in this system). The actual amount of time that the RSA-message will spend in this system will vary between the time you specify in milliseconds and a maximum value calculated by global resource serialization. In this way, global resource serialization balances CPU utilization and ENQ response time. If you omit RESMIL, then the default for the RSA-message residency time is 10 milliseconds.

OFF, if specified, indicates that the RSA-message residency time is zero and that global resource serialization does no tuning. Note that RESMIL(OFF) differs from RESMIL(0). When you specify RESMIL(0), the system tunes the residency time in a range with a minimum of zero.

Value range: 0 to 99999999 milliseconds

Default: 10 milliseconds

RESTART{(YES)|(NO)}: Indicates whether the system defined in the GRSCNFxx MATCHSYS parameter can automatically rebuild a disrupted ring. A disrupted ring occurs when the RSA-message stops moving because of a system failure or a link failure.
Note: If this system is a member of a sysplex, regardless of what you specify, RESTART is set to RESTART(YES).

Default: YES

TOLINT(num): Specifies, in seconds, the maximum tolerance time interval global resource serialization allows the RSA-message to return to that system, before it considers the RSA-message overdue.
When the TOLINT value specified is not valid, then message ISG008E is issued, the TOLINT keyword is ignored, a default of 3 minutes (180 seconds) is used, and the IPL continues.

Value range: The TOLINT value that is specified must be greater than zero (0), and less than 86000 seconds (24 hours).

Default: 180 seconds (3 minutes)

SYNCHRES{(YES)|(NO)}: Indicates whether the system defined in the GRSCNFxx MATCHSYS parameter is to have synchronous reserve processing activated.
Default: YES

Note: If SYNCHRES=YES, but GRS cannot complete the I/O to reserve a device, message ISG363I is issued. The request continues as if SYNCHRES=NO.

[ENQMAXA(value)]

[ENQMAXU(value)]

Identifies the system-wide maximum of concurrent ENQ requests for authorized (ENQMAXA) or unauthorized (ENQMAXU) requesters.

The ENQMAXA range is 250,000 to 99,999,999. The default MAXVALUE is 250,000.

The ENQMAXU range is 16,384 to 99,999,999. The default MAXVALUE is 16,384.

See z/OS MVS Planning: Global Resource Serialization for information about how concurrent ENQ request counts are updated.

[AUTHQLVL(value)]

Indicates the authorized qname level. GRS manages a list of authorized qnames for processing ENQ and DEQ names. If an unauthorized requester attempts to issue an ENQ or DEQ for an authorized qname, GRS fails the request. Although authorized requesters are not required to use qnames from the authorized list, IBM® strongly suggests that they use these qnames to provide protection against "denial-of-service attacks", where an unauthorized requester might obtain a critical ENQ resource and not release it.

As of z/OS® V1R13 IBM recognizes two authorized qname lists. The default list (AUTHQLVL=1) contains the qnames for many IBM products or services that uses them. IBM recognizes a second authorized qname list (AUTHQLVL=2) that includes additional qnames.

For complete information about the contents of these qname lists and ENQ and DEQ processing for authorized qnamess, see "Authorized qnames" in z/OS MVS Planning: Global Resource Serialization.

Use the SETGRS AUTHQLVL to dynamically change the value of the level from 2 to 1.

Use the DISPLAY command to return information about the AUTHQLVL value in effect.

For command syntax information, see z/OS MVS System Commands.

Value range: Either 1 or 2.

Default: 1