DFSMShsm system resources and serialization attributes in a multiple DFSMShsm host environment

Table 1 shows DFSMShsm-related global serialization resources, descriptions of their purposes, and considerations or restrictions on how they are protected.

Global Resource Serialization (GRS) supports two topologies: GRS Ring and GRS Star. A GRS Star requires a coupling facility connected to all hosts in a parallel sysplex. A GRS Ring does not exploit the coupling facility, but requires a common sysplex timer connected to the hosts in or outside of the parallel sysplex. The collection of z/OS images connected in either a GRS Ring or GRS Star topology is termed GRSplex.

The table is divided into four subsections: serialization of control data sets, serialization of functions, serialization of user data sets by DFSMShsm, and serialization of user data sets by the system.

In the table, each pair of QNAME and RNAME values uniquely identifies a resource; the SCOPE indicates the range of control. The DISP (disposition) column indicates whether DFSMShsm or the system requests the resource for exclusive (EXCL) or shared (SHR) use. The significance of the CAN CONVERT FROM RESERVE column is explained in Converting from volume reserves to global resource serialization. The MUST PROPAGATE column indicates whether GRS must communicate the ENQ to all shared systems.

If you use Global Resource Serialization, you can use this table for informational purposes to better understand global serialization. However, if you use a product other than but similar to GRS, you should study this table carefully to determine if you must adapt that product to take particular actions.

Note: The RNAMEDSN parameter may affect the minor names shown in the following table. For a discussion of the RNAMEDSN parameter and GRSplex serialization, see DFSMShsm in a sysplex environment.

Table 1. DFSMShsm-Related Global Serialization Resources
QNAME (MAJOR)	RNAME (MINOR)	SCOPE	DISP	CAN CONVERT FROM RESERVE	MUST PROPAGATE	DESCRIPTION
*SERIALIZATION OF CONTROL DATA SETS*
ARCAUDIT 1	ARCBCDS ARCMCDS ARCOCDS	SYSTEMS	SHR	NO	N.A. 2	The associated volume reserves of the CDS volumes prevent updates from other processors while AUDIT FIX is running in the processor issuing the reserve.
ARCBACK 1	ARCBCDS ARCMCDS ARCOCDS	SYSTEMS	SHR	NO	N.A.	The associated volume reserves of the CDS volumes prevent access or updates to the control data sets from other processors while the control data sets are being backed up in the processor issuing the reserve.
ARCGPA 1	ARCBCDS ARCMCDS ARCOCDS	SYSTEMS	SHR	NO	N.A.	The associated volume reserves of the CDS volumes prevent access or updates to the control data sets from other processors while CDS updates are being made.
ARCGPA	ARCRJRN	SYSTEMS	EXCL	YES	YES	The associated volume reserve of the journal volume prevents access to the journal from other processors while the journal is being read or written in the processor issuing the reserve.
ARCGPAL 1	ARCMCDS	SYSTEMS	SHR	NO	N.A.	The associated volume reserve of the MCDS volume prevents access to the level 2 control record (L2CR) from other processors while the L2CR is being updated in the processor issuing the reserve.
ARCUPDT 1	ARCBCDS ARCMCDS ARCOCDS	SYSTEMS	SHR	NO	N.A.	The associated volume reserves of the CDS volumes prevent access to the control data sets from other processors while they are being recovered by UPDATEC processing in the processor issuing the reserve.
ARCENQG 3	ARCBCDS ARCMCDS ARCOCDS	SYSTEMS	EXCL	N.A.	YES	This enqueue is issued in CDSQ=YES environments and is held while accessing the control data sets from the processor issuing the enqueue.
ARCENQG	ARCCDSVF	SYSTEMS	EXCL	N.A.	YES	This enqueue is issued to ensure that only one CDS version backup function is running in the HSMplex.
ARCENQG	ARCCDSVD	SYSTEMS	EXCL	N.A.	YES	This enqueue is issued to ensure that the data area used in CDS version backup is not updated by any sharing processor while the function is running.
ARCENQG (RLS mode)	ARCCAT	SYSTEMS	SHR	N.A.	YES	This enqueue is issued as a CDS update resource only in RLS mode.
ARCENQG (RLS mode)	ARCCAT	SYSTEMS	EXCL	N.A.	YES	This enqueue is issued as a CDS backup resource only in RLS mode.
*SERIALIZATION OF FUNCTIONS*
ARCENQG	ARCBMBC	SYSTEMS	EXCL	N.A.	YES	This enqueue is issued in SETSYS USERSERIALIZATION environments and ensures that only one instance of move backup versions is running in the HSMplex.
ARCENQG	ARCL1L2	SYSTEMS	EXCL	N.A.	YES	This enqueue is issued in SETSYS USERSERIALIZATION environments and ensures that only one instance of level 1 to level 2 migration is running in the HSMplex.
ARCENQG	ARCMCLN	SYSTEMS	EXCL	N.A.	YES	This enqueue is issued in SETSYS USERSERIALIZATION environments and ensures that only one instance of migration cleanup is running in the HSMplex.
ARCENQG	EXPIREBV	SYSTEMS	EXCL	N.A	YES	There is a limit of one instance of the EXPIREBV command in an HSMplex.
ARCENQG	RECYC-L2	SYSTEMS	EXCL	N.A.	YES	This enqueue is issued during RECYCLE to establish a limit of one instance of recycling ML2 tapes in the HSMplex.
ARCENQG	RECYC-DA	SYSTEMS	EXCL	N.A.	YES	This enqueue is issued during RECYCLE to establish a limit of one instance of recycling daily backup tapes in the HSMplex.
ARCENQG	RECYC-SP	SYSTEMS	EXCL	N.A.	YES	This enqueue is issued during RECYCLE to establish a limit of one instance of recycling spill backup tapes in the HSMplex.
ARCENQG	COPYPOOL\|\| cpname	SYSTEMS	EXCL	N.A.	YES	The scope of the fast replication copy pool extends beyond an HSMplex because a copy pool is defined at the SMSplex level. All DFSMShsm hosts, regardless of which HSMplex they reside in, are prevented from processing the same copy pool. The resource is obtained unconditionally and if the resource is not immediately available, it waits.
ARCENQG	CPDUMP&& cpname&&Vnnn	SYSTEMS	EXCL	N.A.	YES	This enqueue is used for the dumping of copy pools.
ARCBTAPE	volser	SYSTEMS	EXCL	N.A.	YES	This enqueue is used for the Recover Tape Takeaway function.
ARCBTAPE	volser. TAKEAWAY	SYSTEMS	EXCL	N.A.	YES	This enqueue is used for the Recover Tape Takeaway function.
*SERIALIZATION OF USER DATA SETS BY DFSMShsm*
ARCDSN	dsname	SYSTEMS	4	N.A.	YES	For SETSYS USERSERIALIZATION environments, this enqueue enables DFSMShsm to protect the integrity of the data set related to concurrent processing in all HSMplexes. For SETSYS HSERIALIZATION environments, this enqueue enables DFSMShsm to protect the integrity of the data set related to concurrent processing only within the DFSMShsm processor issuing the enqueue.
ARCENQG	dsname	SYSTEMS	5	N.A.	YES	This ENQ prevents catalog locate requests from getting a “not cataloged” response in that interval of time during migration or recall when the volser is being changed from MIGRAT to non-MIGRAT or from non-MIGRAT to MIGRAT. It is also used to determine whether a recall that has an “in process” flag set on really means “in process” or is a residual condition after a system outage.
ARCBACV	volserx 6	SYSTEMS	EXCL	YES	YES	This reserve is issued only when running in a SETSYS HSERIALIZATION environment when doing volume backup. The associated volume reserve of the user volume prevents updates of a user data set from other processors while it is being copied by the processor issuing the reserve.
ARCMIGV	volserx 6	SYSTEMS	EXCL	YES	YES	This reserve is issued only when running in a SETSYS HSERIALIZATION environment when doing volume migration. The associated volume reserve of the user volume prevents updates of a user data set from other processors while it is being copied by the processor issuing the reserve.
*SERIALIZATION OF USER DATA SETS BY THE SYSTEM*
SYSDSN	dsname	7	5	N.A.	YES	This enqueue is the method MVS™ allocation uses to provide data integrity when allocating data sets.
SYSVSAM	dsname	SYSTEMS	5	N.A.	YES	This enqueue is the method VSAM uses to provide data integrity commensurate with the share options of VSAM data sets.
SYSVTOC	volser	SYSTEMS	5	YES	YES	This enqueue is the method DFSMSdfp DADSM uses to provide integrity of a volume’s VTOC. Note: For more information about journal volume dumps, see DFSMSdss Considerations for dumping the journal volume.
1 These resources are requested only in CDSR=YES environments. In CDSQ=YES environments, serialization is achieved via a global enqueue using the QNAME of ARCENQG. 2 N.A. means Not applicable 3 Valid if CDSQ = YES 4 EXCL is used for migration, recall, recover, and ARECOVER. SHR is used for backup and ABACKUP. 5 The DISP of this resource can be either EXCL or SHR. There are some requests of each type. 6 Used only in SETSYS DFHSMDATASETSERIALIZATION 7 The SCOPE of the SYSDSN resource is SYSTEM only but is automatically propagated by GRS, if the default GRSRNL00 member supplied by MVS is being used. GRS-equivalent products also need to propagate this resource.