Syed Saad Ali
Syed Saad Ali
Author: Syed Saad Ali
September 1, 2017
Oracle RAC Daemons and Processes
Installation/Configurations10gInstallation/Configurations11gInstallation/Configurations12cOracle Database Material
Oracle RAC Daemons and Processes
OPROCd |
Process Monitor | provides basic cluster integrity services |
EVMd |
Event Management | spawns a child process event logger and generates callouts |
OCSSd |
Cluster Synchronization Services | basic node membership, group services, basic locking |
CRSd |
Cluster Ready Services | resource monitoring, failover and node recovery |
LMSn |
Lock Manager Server process – GCS | this is the cache fusion part, it handles the consistent copies of blocks that are tranferred between instances. It receives requests from LMD to perform lock requests. I rools back any uncommitted transactions. There can be upto ten LMS processes running and can be started dynamically if demand requires it. they manage lock manager service requests for GCS resources and send them to a service queue to be handled by the LMSn process. It also handles global deadlock detection and monitors for lock conversion timeouts. |
LMON |
Lock Monitor Process – GES | this process manages the GES, it maintains consistency of GCS memory in case of process death. It is also responsible for cluster reconfiguration and locks reconfiguration (node joining or leaving), it checks for instance deaths and listens for local messaging. A detailed log file is created that tracks any reconfigurations that have happened. |
LMD |
Lock Manager Daemon – GES | this manages the enqueue manager service requests for the GCS. It also handles deadlock detention and remote resource requests from other instances. |
LCK0 |
Lock Process – GES | manages instance resource requests and cross-instance call operations for shared resources. It builds a list of invalid lock elements and validates lock elements during recovery. |
DIAG |
Diagnostic Daemon | This is a lightweight process, it uses the DIAG framework to monitor the healt of the cluster. It captures information for later diagnosis in the event of failures. It will perform any neccessary recovery if an operational hang is detected. |
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RAC Useful Parameters
Installation/Configurations10gInstallation/Configurations11gInstallation/Configurations12cOracle Database Material
RAC Useful Parameters
| cluster_interconnects | specify a specific IP address to use for the inetrconnect |
| _gcs_fast_config | enables fast reconfiguration for gcs locks (true|false) |
| _lm_master_weight | controls which instance will hold or (re)master more resources than others |
| _gcs_resources | controls the number of resources an instance will master at a time |
| _lm_tickets | controls the number of message tickets |
| _lm_ticket_active_sendback | controls the number of message tickets (aggressive messaging) |
| _db_block_max_cr_dba | limits the number of CR copies per DBA on the buffer cache (see grd) |
| _fairness_threshold | used when too many CR requested arrive for a particular buffer and the block becomes disowned (see grd) |
| _gc_affinity_time | specifies interval minutes for reamstering |
| _gc_affinity_limit | defines the number of times a instance access the resource before remastering |
| _gc_affinity_minimum | defines the minimum number of times a instance access the resource before remastering |
| _lm_file_affinity | disables dynamic remastering for the objects belonging to those files |
| _lm_dynamic_remastering | enable or disable remastering |
| _gc_defer_time | define the time by which an instance deferred downgrading a lock (see Cache Fusion) |
| _lgwr_async_broadcast | change the SCN boardcast method (see troubleshooting) |