Overview
The information about wait events is displayed in the following dynamic performance views:
V$SESSION_WAIT: displays the current or last wait events of sessions.V$SYSTEM_EVENT: displays all wait events of the current tenant.V$SESSION_EVENT: displays all wait events for each session. This view is similar toV$SYSTEM_EVENT.
Many wait events are associated with internal implementation, and therefore may be deleted or changed. The actual wait events shall prevail.
Wait event classes
Each wait event belongs to a specific class of wait event. Wait events are classified into the following classes:
| Wait Event Type | Type ID | Description |
|---|---|---|
| OTHER | 100 | The wait events that do not belong to any other type. |
| APPLICATION | 101 | The wait events caused by client-side code. |
| CONFIGURATION | 102 | The wait events caused by insufficient database or instance resource configurations. |
| ADMINISTRATIVE | 103 | The user wait events caused by commands entered by the database administrator. |
| CONCURRENCY | 104 | The wait events related to internal database resource contention. |
| COMMIT | 105 | The wait events related to log commit. |
| IDLE | 106 | The wait events that occur when a session is inactive and waiting for a specific task to be executed. |
| NETWORK | 107 | The wait events related to network communication. |
| USER_IO | 108 | The wait events related to user I/O. |
| SYSTEM_IO | 109 | The wait events related to background process I/O. |
| CLUSTER | 111 | The wait events related to clusters. |
View wait events
You can execute SQL statements under the system tenant to display all wait events and their classes in alphabetical order. Here is an example:
obclient> SELECT name, wait_class FROM V$EVENT_NAME ORDER BY name;
General wait events
| Event name | Description | Event class | First parameter | Second parameter | Third parameter |
|---|---|---|---|---|---|
| wait remove partition | The event of waiting for the deletion of partitions to complete. | ADMINISTRATIVE | tenant_id | table_id | partition_id |
| wait end stmt | The event of waiting for a statement to end. | CLUSTER | rollback | trans_hash_value | physic_plan_type |
| wait start stmt | The event of waiting for a statement to start. | CLUSTER | trans_hash_value | physic_plan_type | participant_count |
| wait end trans | The event of waiting for a transaction to commit. | COMMIT | rollback | trans_hash_value | participant_count |
| async rpc proxy condition wait | The asynchronous RPC wait event in top-level encapsulation. | CONCURRENCY | address | - | - |
| dag worker condition wait | The dag thread wait event in the background. | CONCURRENCY | address | - | - |
| latch: alive server tracer lock wait | The event of waiting for the OBServer status lock in the OBAliveServerMap operation memory. |
CONCURRENCY | address | number | tries |
| latch: alloc object lock wait | The lock wait event during the management of small memory blocks in OceanBase Database by using the malloc() function. | CONCURRENCY | address | number | tries |
| latch: clog cascading info lock wait | The lock wait event of the clog replica cascading module. | CONCURRENCY | address | number | tries |
| latch: clog locality lock wait | The event of waiting for the lock of locality information for internal protection of clogs. | CONCURRENCY | address | number | tries |
| latch: clog task lock wait | The event of waiting for the log_task lock of the clog module. | CONCURRENCY | address | number | tries |
| latch: config lock wait | The event of waiting for the parameter lock. | CONCURRENCY | address | number | tries |
| latch: default drw lock wait | The DRW lock wait event. The DRW lock is a read-write lock that adapts to scenarios with many read operations and few write operations. | CONCURRENCY | address | number | tries |
| latch: default mutex wait | The default mutex wait event. | CONCURRENCY | address | number | tries |
| latch: default recursive mutex wait | The default recursive mutex wait event. | CONCURRENCY | address | number | tries |
| latch: default spin lock wait | The default spin lock wait event. | CONCURRENCY | address | number | tries |
| latch: default spin rwlock wait | The default spin read-write lock wait event. | CONCURRENCY | address | number | tries |
| latch: id map node lock wait | The ID Map wait event. The ID Map maps integers to pointers. | CONCURRENCY | address | number | tries |
| latch: server maintaince lock wait | The lock wait event when the RootServer (RS) performs an operation on an OBServer node. | CONCURRENCY | address | number | tries |
| latch: server status lock wait | The read-write lock wait event when an operation is performed on server_statuses recorded by the RS. | CONCURRENCY | address | number | tries |
| latch: unit manager lock wait | The lock wait event when the Unit Manager operates on data. | CONCURRENCY | address | number | tries |
| latch: zone infos rw lock wait | The lock wait event when OBZoneManagerBase operates on data. | CONCURRENCY | address | number | tries |
| latch: zone manager maintaince lock wait | The lock wait event when the Zone Manager operates on data. | CONCURRENCY | address | number | tries |
| partition table updater condition wait | The conditional wait event when OBUniqTaskQueue processes tasks. | CONCURRENCY | address | - | - |
| rebalance task mgr condition wait | The conditional wait event when OBDRTaskMgr processes disaster recovery tasks. | CONCURRENCY | address | - | - |
| reentrant thread condition wait | The conditional wait event when OBReentrantThread processes tasks. | CONCURRENCY | address | - | - |
| rpc session handler condition wait | The streaming RPC wait event. | CONCURRENCY | address | - | - |
| th worker condition wait | The multi-tenant thread suspension wait event. | CONCURRENCY | address | - | - |
| thread idling condition wait | The RootService idle thread wait event. | CONCURRENCY | address | - | - |
| sched idle | The task execution wait event of the multi-tenant thread. | IDLE | wait start timestamp | - | - |
| mysql response wait client | The client response wait event. | NETWORK | - | - | - |
| sync rpc | The synchronization RPC wait event. | NETWORK | pcode | size | - |
| sched wait | The event of waiting for the multi-tenant thread to execute large queries. | SCHEDULER | req type | req start timestamp | wait start timestamp |
| bloomfilter build read | The event of waiting for the background BloomFilter to build data read operation. | SYSTEM_IO | fd | offset | size |
| db file compact read | The event of waiting for data read in a compaction task. | SYSTEM_IO | fd | offset | size |
| db file compact write | The event of waiting for data write in a compaction task. | SYSTEM_IO | fd | offset | size |
| db file index build read | The event of waiting for index building and reading for the database file. | SYSTEM_IO | fd | offset | size |
| db file index build write | The event of waiting for index building and writing for the database file. | SYSTEM_IO | fd | offset | size |
| db file migrate read | The migration data read wait event. | SYSTEM_IO | fd | offset | size |
| db file migrate write | The migration data write wait event. | SYSTEM_IO | fd | offset | size |
| memstore memory page alloc wait | The event of waiting for MemStore write throttling to be triggered. | SYSTEM_IO | cur_mem_hold | sleep_interval | cur_ts |
| db file data read | The event of reading user data. | USER_IO | fd | offset | size |
| interm result disk read | The event of reading intermediate result data. | USER_IO | fd | offset | size |
| interm result disk write | The event of writing intermediate result data. | USER_IO | fd | offset | size |
| row store disk read | The event of reading SQL operator data from the disk. | USER_IO | fd | offset | size |
| row store disk write | The event of writing SQL operator data to the disk. | USER_IO | fd | offset | size |
| build index scheduler condition wait | The wait before DDL task scheduling is performed again. | CONCURRENCY | address | - | - |
| debug sync condition wait | This event is meaningful only in Errsim debug mode and is meaningless in user scenarios. | CONCURRENCY | address | - | - |
| inner connection pool condition wait | The conditional wait event of the internal connection pool. | CONCURRENCY | address | - | - |
| latch: bandwidth throttle lock wait | The bandwidth throttling lock wait event. | CONCURRENCY | address | number | tries |
| latch: default bucket lock wait | The bucket lock wait event, which is not classified. | CONCURRENCY | address | number | tries |
| latch: election group trace recorder lock wait | The event of waiting for the lock that protects the election group trace information. | CONCURRENCY | address | number | tries |
| latch: group migrate lock wait | The batch migration lock wait event. | CONCURRENCY | address | number | tries |
| latch: group migrate task lock wait | The task lock wait event in batch migration. | CONCURRENCY | address | number | tries |
| latch: io queue lock wait | The lock wait event in I/O queue reads. | CONCURRENCY | address | number | tries |
| latch: migrate lock wait | The lock wait event in migration. | CONCURRENCY | address | number | tries |
| latch: multi tenant lock wait | The lock wait event in multi-tenant management. | CONCURRENCY | address | number | tries |
| latch: rebuild retry list lock wait | The rebuild task lock wait event. | CONCURRENCY | address | number | tries |
| latch: session trace recorder lock wait | The trace record lock wait event in a session. | CONCURRENCY | address | number | tries |
| latch: tenant lock wait | The event of waiting for the lock for tenant management. | CONCURRENCY | address | number | tries |
| latch: timezone lock wait | The Timezone structure lock wait event in a tenant. The lock is added for a tenant operation. | CONCURRENCY | address | number | tries |
| oblog part mgr schema version wait | The event of waiting for the liboblog to refresh the schema version logic. | CONCURRENCY | - | - | - |
| server object pool arena lock wait | The event of waiting for the lock of large object cache structures. | USER_IO | fd | offset | size |
| async commiting wait | The event of waiting for the asynchronous commit of clogs. | COMMIT | - | - | - |
| exec inner sql wait | The event of waiting for the execution of internal SQL statements. | OTHER | wait inner sql class | inner session id | - |
| sync rpc | The synchronization RPC wait event. | NETWORK | pcode | size | - |
| sleep: wait refresh schema | The event of waiting for the schema to refresh to the specified version. | CONFIGURATION | sleep_interval | schema_version | - |
| palf throttling sleep | The event of throttling log threads. | USER_IO | sleep_interval | - | - |
| palf read | The event of waiting for the log thread to write logs. | SYSTEM_IO | fd | offset | size |
| palf write | The event of waiting for the log thread to read logs. | SYSTEM_IO | fd | offset | size |