Data Sharing Locking Activity window

Use the Data Sharing Locking Activity window to view statistical information about data sharing locking activity for the DB2® subsystem.

To display this window, select Data Sharing Locking Activity from the Db2 Statistics Detail panel. This selection is only available if the monitored Db2 subsystem is part of a data sharing group.
Figure 1. Data Sharing Locking Activity window
 DGOMSWSL          Data Sharing Locking Activity


                                                      More:     +
 Global contention rate (%)  . . . . . . . . . . . . . :        0

 P-locks
   Lock requests . . . . . . . . . . . . . . . . . . . :      N/P
   Unlock requests . . . . . . . . . . . . . . . . . . :      N/P
   Change requests . . . . . . . . . . . . . . . . . . :        0


 Synchronous XES
   Lock requests . . . . . . . . . . . . . . . . . . . :      625
   Unlock requests . . . . . . . . . . . . . . . . . . :      554
   Change requests . . . . . . . . . . . . . . . . . . :     11.4
 Asynchronous XES
   Resources . . . . . . . . . . . . . . . . . . . . . :        3

 Suspensions
   IRLM global contention  . . . . . . . . . . . . . . :       17
   XES global contention . . . . . . . . . . . . . . . :       12
   False contention and conversion . . . . . . . . . . :        0
     False contention  . . . . . . . . . . . . . . . . :        0
 Incompatible retained lock  . . . . . . . . . . . . . :       39

 Notify messages sent  . . . . . . . . . . . . . . . . :        0
 Notify messages received  . . . . . . . . . . . . . . :      128
 P-lock/notify exists
   Maximum engines . . . . . . . . . . . . . . . . . . :       11
   Engines unavailable . . . . . . . . . . . . . . . . :     11.6

 P-lock negotiation
   Pageset/partition . . . . . . . . . . . . . . . . . :     1127
   Page  . . . . . . . . . . . . . . . . . . . . . . . :      132
   Other . . . . . . . . . . . . . . . . . . . . . . . :      8.5
   Change. . . . . . . . . . . . . . . . . . . . . . . :      523
 Command ===> ___________________________________________________
  F1=Help      F2=Split     F3=Exit      F5=Auto      F6=History
  F7=Up        F8=Down      F9=Swap     F10=Delta    F11=Interval
 F12=Cancel   F16=Look     F17=Collect

A logical lock (L-lock) is a lock used by transactions to control intra-DB2 and inter-DB2 data concurrency between transactions. A physical lock (P-lock) is a lock used only by data sharing and is acquired by Db2 to provide consistency on data cached in different Db2 subsystems. P-locks are owned by the subsystem, not by the transaction. XES is the Cross System Extended Services component of MVS. For more information about locking in a data sharing environment, see Db2 Data Sharing: Planning and Administration.

The following list describes the fields shown in this window:
Global contention rate (%)
The total number of suspends because of contention, divided by the total number of requests that went to XES (excluding asynchronous requests), multiplied by 100.
P-locks -- Lock requests
The number of lock requests for P-locks.
P-locks - Unlock requests
The number of unlock requests for P-locks.
P-locks - Change requests
The number of change requests for P-locks.
Synchronous XES - Lock requests
The number of lock requests propagated to MVS XES synchronously.
Synchronous XES - Unlock requests
The number of resources synchronously propagated to MVS XES by unlock requests.
Synchronous XES - Change requests
The number of change requests propagated to MVS XES synchronously.
Asynchronous XES - Resources
The number of resources propagated to MVS XES asynchronously by IRLM.
Suspensions - IRLM global contention
The number of suspensions because of IRLM global contention. IRLM lock states were in conflict.
Suspensions - XES global contention
The number of suspensions because of MVS XES global contention. MVS XES lock states were in conflict, but IRLM was not.
Suspensions - False contention and conversion
Summation of false contentions (see below) and sync-to-async heuristic conversions. Conversions are done when XES determines that it is more efficient to drive the request asynchronously to the CF.
False contention
The number of false contentions encountered on this z/OS® image. A false contention occurs when different resource names hash to the same entry in the CF lock table. The CF detects contention within the hash entry, and XES uses inter-system messaging to determine that no actual resource contention exists. This counter is maintained on a per-LPAR basis. Therefore this counter over-reports false contentions in cases where multiple members from the same data sharing group run on the same z/OS image. The counter is not present (N/P) if data is unavailable because of errors from the IXLMG service.
Incompatible retained lock
The number of global lock or change requests rejected or suspended because of an incompatible retained lock.
Notify messages sent
The number of notify messages sent.
Notify messages received
The number of notify messages received.
P-lock⁄notify exits - Maximum engines
The maximum number of engines available for P-lock exit or notify exit requests.
P-lock⁄notify exits - Engines unavailable
The number of times an engine is not available for P-lock exit or notify exit requests.
P-lock negotiation - Pageset⁄partition
The number of times this Db2 was driven to negotiate a page set or partition P-lock because of changing inter-DB2 interest levels on the page set or partition.
P-lock negotiation - Page
The number of times this Db2 was driven to negotiate a page P-lock because of inter-DB2 P-lock contention.
P-lock negotiation - Other
The number of times this Db2 was driven to negotiate another P-lock type (other than pageset⁄partition or page).
P-lock negotiation - Change
The number of times a P-lock change request was issued during P-lock negotiation.