Know more about RAC GES STATISTICS

GES 全称为Global Enqueue Services是RAC中重要的全局队列锁服务,V$GES_STATISTICS 动态性能视图汇聚了主要的GES STATISTICS 统计信息。为了更好地理解GES STATISTICS ,我们可以通过下表理解这些统计项的含义:




0 messages sent directly         


Incremented when any process successfully sends a message to a remote instance without being blocked and without flow control.


1 messages flow controlled                 


Incremented when any process could not send a message directly because there were not enough tickets available.


2 messages sent indirectly


Incremented when any process is asked to flow-control the message (i.e. a process tried to send a message indirectly, even if a ticket was available). This can also be incremented when previous message to the same target node had failed or a GCS/GES operation is being frozen.


3 messages received logical


When LMS receives a GCS/GES message from remote or local client, this statistic is incremented.


61 messages received actual


When LMS receives a message from a remote instance, this is incremented. A single actual message can contain multiple logical messages. Note, that when remote messages are queued, because they are flow controlled or they are indirectly / intentionally queued, the LMS process tries to send them in batch instead of flushing them individually.


4 flow control messages sent

5 flow control messages received


Messages flow controlled due to lack of ticket.


6 gcs msgs received

7 gcs msgs process time(ms)

8 ges msgs received

9 ges process time(ms)


When LMS receives a message, and if the message is related to either GCS (Global Cache Service) or GES (Global Enqueue Service) activity, it is incremented. After a GCS/GES message is processed, the process (typically LMD or LMS) updates the following statistics.


  • gcs msgs received
  • gcs msgs process time(ms)
  • ges msgs received
  • ges msgs process time(ms)


10 msgs causing lmd to send msgs 

11 lmd msg send time(ms)

65 msgs causing lms to send msgs 

66 lms msg send time(ms)


Incremented when the LMD/LMS processes a GCS/GES message and it causes LMD/LMS to send one or more messages. For example, if LMS receives a message, and as part of processing it sends four more messages, the statistic will be incremented by 1, not 4. In order to get the exact number of messages sent by LMS, the session statistic ‘gcs messages sent’ and ‘ges messages sent’ needs to be retrieved for the session running LMS (from V$SESSTAT).


12 gcs side channel msgs actual

13 gcs side channel msgs logical


‘side channel msgs logical’ indicates the number of blocks shipped from this node to other nodes. ‘side channel msgs actual’ indicates the actual number of messages sent to other nodes. When CR blocks or current blocks are sent to a remote node, the sender actually sends another reliable message to the requestor, because the CR block or current block being shipped could be lost. For example, a node sends 100 CR blocks to another node (logical number of messages). The sender node then may send a message saying ‘I’ve sent 100 blocks’ in a single message (actual number of messages). The init.ora parameter ‘_side_channel_batch_size’ defines the number of side channel messages to be sent in a single message.  With reliable IPC technology such as RSM and HyperFabric, we do not need side channel messages, and this value should be 0. With non-reliable IPC technology like UDP, these should be increased.


14 gcs pings refused


Incremented when the master node sends a BAST to a holder node, and the holder node is not able to service the BAST for some reason (typically because the block is not present or the ping queue is full).


15 gcs writes refused


Same as above, except that this is for Writes. In RAC if the blocks are globally dirty the writes are mediated by the GCS.


16 gcs error msgs


Certain race conditions in the GCS this statistic to be updated. It usually involves sending some extra messages to resolve the race through the use of error messages.


17 gcs out-of-order msgs


With direct sends, it is possible for two messages, which are sent from the same instance, to be received out-of-order at the master node. This statistic is updated whenever that happens.


18 gcs immediate (null) converts


Incremented when NULL lock can be granted immediately


19 gcs immediate cr (null) converts


Incremented when NULL lock for CR request can be granted immediately


20 gcs immediate (compatible) converts


Incremented when shared lock can be granted immediately


21 gcs immediate cr (compatible) converts


Incremented when shared lock for CR request can be granted immediately


22 gcs blocked converts


Incremented when the lock cannot be granted immediately. The lock is on the head of the convert queue.


23 gcs queued converts


Incremented when the lock cannot be granted immediately, and there is a conflicting lock in the convert queue ahead of this lock.


24 gcs blocked cr converts


Incremented when a CR request cannot be granted a lock because the lock is already being converted or the lock is in exclusive mode


25 gcs compatible basts


Number of BAST’s sent to holder node of a compatible lock.


26 gcs compatible cr basts (local)


CR request can be granted a lock, and BAST is sent to holder node. The lock is in local role.


60 gcs compatible cr basts (global)


This is incremented when the lock request is compatible but we can’t read from
disk because the block is globally dirty.


27 gcs cr basts to PIs


CR request is sent to an instance that has a PI buffer that satisfies this CR request.


28 dynamically allocated gcs resources

29 dynamically allocated gcs shadows


Number of gcs resources / shadows dynamically allocated after the startup of instance. We should not see these increasing at all.  _gcs_resources and _gcs_shadows could be used to change the default number of these resources to avoid dynamic allocation, but we should treat it as a bug (the default should be enough or it could be memory leak.).


30 gcs recovery claim msgs


Number of recovery claim messages processed by this instance.


31 gcs indirect ast


AST is sent to LMS instead of foreground process.


32 gcs dbwr write request msgs

33 gcs dbwr flush pi msgs

34 gcs lms write request msgs

35 gcs lms flush pi msgs

36 gcs write notification msgs


Messages related to flushing dirty XCUR / PI buffers. To flush PI buffers, request master node to write the most recent copy of the block in the global cache, which is ‘write request msgs’. Once the most recent copy of the block in the global cache is written to disk, PI buffers in the global cache can be purged, which is ‘flush pi msgs’. Once the most recent copy is written to disk, ‘write notification’ message is sent to the master node.


37 gcs retry convert request


Convert request had to be retried due to some race conditions.


38 gcs regular cr


CR for data blocks


39 gcs undo cr


CR for undo blocks


40 gcs assume no cvt


Assume was processed when the convert q is empty.


41 gcs assume cvt


Assume was processed when the convert q is non-empty.


42 broadcast msgs on commit(actual)


MCPD=0, number of messages sent to update the SCN.


43 broadcast msgs on commit(logical)


Same as 42, but logical (because the update may have been piggybacked).


44 broadcast msgs on commit(wasted)


Update SCN mesage is sent, but it is potentially a waste because receiver may have already updated the SCN.


45 acks for commit broadcast(actual)

46 acks for commit broadcast(logical)


Same as 42, 43 except that it applies to the receiving instance.


47 false posts waiting for scn acks


We posted LGWR because we thought MCPD broadcast completed, but it didn’t.


48 gcs forward cr to pinged instance


CR request is forwarded to the instance that is currently converting the GCS resource


49 gcs cr serve without current lock


CR block is served by the instance that does not have the current lock.


50 msgs sent queued

51 msgs sent queue time (ms)


Number of logical messages sent through send queue and their queuing time. Queuing time for queued messages: ‘msgs sent queue time (ms)’ / ‘msgs sent queued’  à Average message queuing time for flow controlled or indirectly sent messages. Note: this is calculated at ‘kjct’ layer (GCS/GES communication layer).


52 msgs sent queued on ksxp

53 msgs sent queue time on ksxp (ms)


Number of messages queued, and queuing time on ksxp layer. This includes all types of GCS/GES messages sent by any Oracle processes (foreground and background processes). Note: ‘msgs sent queued’ is a statistic from the kjct layer where we know if the messages are directly sent or indirectly sent.


54 msgs received queue time (ms)

55 msgs received queued


Elapsed time that a message is actually received until it is processed. Number of messages received  (logical). The ratio ‘msgs received queue time (ms)’ / ‘msgs received queued’ gives us the average queuing time between message arrival and start processing.


56 implicit batch messages sent

57 implicit batch messages received


Number of messages sent/received that are batched implicitly. Note: messages that are queued because of flow control or because of indirect messages, can be batched.


58 gcs refuse xid


Number of lock request received but refused to process by this instance, because index split is in progress (new in Oracle9i Release 2)


59 gcs ast xid


Number of lock request canceled because of index split


62 process batch messages sent

63 process batch messages received


Number of messages sent/received in batch.  When LMS receives multiple remote messages at a time, it processes all of them first, and then sends messages in batch as a result, instead of sending the result for each request individually.


64 messages sent pbatched


This is the number of messages being sent through process batching. This is the logical number whereas “process batch messages sent” is the actual number of messages sent out. Process batching in 10g is used for multi-block read, newing, receiver direct send (LMD0, LMS*, LMON) and fusion write (DBW*).


67 global posts requested


AQ requested that a global post be delivered to another instance


68 global posts dropped


Post was dropped because there was no buffer space.


69 global posts queued


A post was queued to be sent to another instance


70 global posts sent


A post was actually sent to another instance


71 global posts queue time


Time difference between enqueuing and sending the post.


72 messages sent not implicit batched


This is the number of indirect sent messages not get any batching done from the send proxies due to various reason. For example, the message is big enough or is defined as non-batch type.


73 messages queue sent actual


Actual number of messages sent indirectly by send proxies.


74 messages queue sent logical


Logical number of messages sent indirectly by send proxies including the number of embedded message batched either through process batching or batching done in send proxies.






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