Lock Detail - P-Lock Requests
This section shows the event specific data for P-Lock requests.
- Page set or partition P-Lock request or page set or partition
P-Lock negotiation request
These P-Locks track inter-DB2 interest on a linear page set (table space or index) or a partition of a partitioned page set.
The cached state of the page set or partition P-Lock tells DB2® which data sharing protocols must be used to maintain inter-DB2 buffer coherency for the page set or partition. For example, a cached state of IS tells DB2 that whenever a page belonging to that page set or partition is read into the buffer pool, the page must be registered to the coupling facility for cross-invalidation purposes. If the cached state were SIX, the coupling facility page registration would not be necessary.
Normally the P-Lock is held by DB2 in the cached state. The P-Lock state determines whether or not the page set or partition is GBP-dependent:- If the page set or partition P-Lock is held in S or X, then the page set or partition is not GBP-dependent.
- Otherwise, the page set or partition is GBP-dependent.
- Page P-Lock request or page P-Lock negotiation request
These P-Locks preserve the inter-DB2 cached page (buffer) coherency when row level locking is used and the page set or partition is actively R/W shared between two or more DB2 systems. The most common cases of subpage concurrency are row-level locking.
The format of the data for these events is shown in Format of Page Set or Partition P-Lock Requests and Format of Page P-Lock Requests.
Format of Page Set or Partition P-Lock Requests
The following example shows the format of the data for this event.
REQUEST=xxxxxx OBJECT=xxxxxxxxxxx
MEMBER =xxxxxxxx REQUESTED STATE =xxxxx
OLD STATE=xxxxx OLD CACHED STATE=xxxxx
NEW STATE=xxxxx NEW CACHED STATE=xxxxx
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Format of Page P-Lock Requests
The following example shows the format of the data for this event.
REQUEST=xxxxxx OBJECT=xxxxxxxxxxxxxxx
MEMBER =xxxxxxxx REQUESTED STATE=xxxxx
OLD STATE=xxxxx NEW STATE=xxxxx
aaaaaaaaaaaaaaaaaaaaaaaa
Field description
- REQUEST
- The IRLM request type, which can be one of the following:
- LOCK
- UNLOCK
- CHANGE
- EXIT
- OBJECT
- The DB2 object type, which can be one of the following:
- TABLESPACE
- INDEXSPACE
- DATA PAGE
- HEADER PAGE
- INDEX PAGE
- SPACE MAP PAGE
- MEMBER
- A DB2 member name that depends on the request type:
- For exit requests, the name of the DB2 member in conflict with this member's currently held P-Lock state.
- For lock, unlock, and change requests, for which P-Lock is rejected, the name of the DB2 member in conflict with this request.
- REQUESTED STATE
- The requested lock state. It only applies to lock, change, and
exit requests.
For exit requests, this is the P-Lock state requested by the member causing the P-Lock exit of this member. If the request from the other member was not in conflict with the state of this member, this field shows NH.
The values for this field are shown in Table 1.
Table 1. Lock State State Description NH Not held IS This DB2 has R/O interest on the page set or partition and one or more other DB2s in the group have R/W interest IX This DB2 has R/W interest on the page set or partition, one or more other DB2s in the group have R/O interest, and one or more can also have R/O interest S This DB2 has R/O interest on the page set or partition and no other DB2 in the group has R/W interest but one or more can have R/O interest SIX This DB2 has R/W interest on the page set or partition and no other DB2 in the group has R/W interest but one or more can have R/O interest NSU Nonshared update X This DB2 has R/W interest on the page set or partition and no other DB2 in the group has any interest RD Request denied - OLD STATE
- The previously held P-Lock state.
The values for this field are shown in Table 1.
- NEW STATE
- The newly held P-Lock state.
The values for this field are shown in Table 1.
- OLD CACHED STATE
- The previous P-Lock cached state.
The values for this field are shown in Table 1.
- NEW CACHED STATE
- The new P-Lock cached state.
The values for this field are shown in Table 1.
- aaaaaaaaaaaaaaaaaaaaaaaa
- Stands for the P-Lock attributes, which can be one or more of
the following:
- UNCONDITIONAL or CONDITIONAL.
- RESTART or NONRESTART. Such a request instructs IRLM to convert a retained lock held by the DB2 system into an active lock. If the requested lock is not retained, IRLM grants the request as normal.
- MODIFY or NONMODIFY.