Enqueue/Reserve Process

The for z/OS products enqueue (ENQ) and reserve (RESERVE) resources, depending on the:
capan146
The
Panvalet
for z/OS products enqueue (ENQ) and reserve (RESERVE) resources, depending on the:
  • Libraries being used
  • Panvalet
    commands being processed
  • Installation options chosen
  • Panvalet
    product or option being used
  • Method of defining DASD to the z/OS systems
This section covers the following topics:
Library Protection
Normally, an exclusive system enqueue is issued for the
Panvalet
libraries for the duration of the
Panvalet
job to prevent other
Panvalet
tasks on the same CPU from updating the
Panvalet
library at the same time. This exclusive resource control is needed not only for the various commands that could update members but also to allow the update of Data of Last Access as members are referred to for read-only processing. This exclusive control mechanism could cause performance problems and even lockouts during processing, especially in shared DASD (multiple CPU) sites or where concatenated
Panvalet
data sets are used extensively. The following explains how the system works and some alternative methods for reducing performance and lockout problems.
The following ENQ parameters are used:
  • Qname (PANVALET)
  • Rname (data set name of
    Panvalet
    library (length= 44))
  • Scope (SYSTEM)
PANVALET locks out users from the same CPU.
If the
Panvalet
library resides on a DASD unit that is generated to z/OS as shared (UCB UCBTBYT2 = UCBRR/UCB2OPT2), then in addition to the above ENQ, an exclusive reserve is issued on that
Panvalet
library. The following RESERVE parameters are used:
  • Qname (VALETPAN)
  • Rname (data set name of
    Panvalet
    library (length= 44))
  • Scope (SYSTEMS)
VALETPAN locks out users from either CPU.
The RESERVE prevents more than one CPU from updating the
Panvalet
library at the same time.
If the
Panvalet
library resides on DASD that is shared between two or more CPUs, and any of those CPUs do not have that DASD generated as shared, then the library is not protected from possible integrity problems caused by multiple CPUs updating the library at the same time.
A RESERVE can not only lock out other CPUs (users) from accessing the
Panvalet
library being updated, but also prevent their access to anything else on that pack. The length of time a DASD device is locked out to other CPUs can range from short to long, depending on the
Panvalet
processing selected by a user on the CPU that issued the RESERVE.
For example, a PAN#8 SCAN of a very large
Panvalet
library could RESERVE a
Panvalet
library for several minutes, whereas a PAN#1 WRITE to print of a small member would RESERVE a library for less than a second.
If you are certain your batch input command stream does not require any updates, you can use the EXEC PARM 'OPEN=INP' for certain commands to prevent any ENQs and RESERVEs from being issued. See Read-Only Access in Executing PAN#1 for more information.
To address this situation,
Panvalet
has a footprinting option to minimize the effects of locking up full DASD packs for long lengths of time. During processing,
Panvalet
batch input commands could require an update to take place to a member or directory of a
Panvalet
library.
When the footprinting option is selected (FTP=YES), the DASD packs (generated as shared to z/OS) are RESERVED just long enough to update the control record of the
Panvalet
library, thereby minimizing the effects of full pack RESERVEs.
The
Panvalet
ISPF Option uses this process for very short durations. For more information, see Member Protection later in this section.
The following provides recommended definitions to define
Panvalet
QNAMES to Global Resource Serialization (GRS):
RNLDEF RNL(INCL) TYPE(GENERIC) QNAME(PANVALET) RNLDEF RNL(CON) TYPE(GENERIC) QNAME(VALETPAN) RNLDEF RNL(INCL) TYPE(GENERIC) QNAME(SPFPAN) RNLDEF RNL(CON) TYPE(GENERIC) QNAME(SPFEDIT)
Partitioned Data Set Protection
A conditional exclusive step enqueue is issued against the partitioned data set for reading and writing members (++OPTION INPUT,++OPTION OUTPUT).
Qname - SPFEDIT Rname - Data set name of PDS (length= 44)
A conditional exclusive SYSTEMS enqueue is issued against the directory of the partitioned data set during BLDL and STOW functions to prevent conflict with SPF(TSO). This also enqueues on the partitioned data set directory, using the same Qname and Rname.
Qname - SPFEDIT Rname - Data set name of PDS plus PDS member name (length= 52)
Panvalet
batch and the
Panvalet
TSO Option use this process.
Member Protection
An exclusive conditional system ENQUEUE is issued against a given
Panvalet
member during an EDIT or BROWSE function to prevent conflict with other
Panvalet
ISPF Option users trying to perform the same functions on that member.
Qname - SPFPAN Rname - Data set name of CA-Panvalet library plus member name (length= 54)
The
Panvalet
ISPF Option uses this process.
The
Panvalet
ISPF Option uses the ENQ/RESERVE process defined in Library Protection in this section. However, this ENQ/RESERVE is of very short duration; it is issued only during the specific member or directory write to the file by the
Panvalet
ISPF Option. For more information about simultaneous update protection, see Option for CMS, ISPF, and TSO.
The following provides suggested definitions to define
Panvalet
QNAMES to Multi-Image Manager (MIM):
GDIF=YES, /* GDIF SHOULD PROCESS THIS SCOPE=SYSTEM, /* ALL ENQS PROCESSED BY GDIF EXEMPT=NO, /* EXEMPT LIST OPTION ECMF=NO, /* ECMF REPORTS CONFLICTS RPTAFTER=0, /* REPORT CONFLICT IMMEDIATELY RPTCYCLE=60, /* AND EVERY 60 SECONDS THEREAFTER TRACE=CONFLICT /* TRACE OPTION
We strongly recommend that you use SCOPE=SYSTEM in your MIM definition.