Waiting to read or update replication slot state. Waiting to allocate a new transaction ID. See, One row per database, showing database-wide statistics about query cancels due to conflict with recovery on standby servers. Waiting to acquire an exclusive pin on a buffer. LWLock- buffer_mapping. This includes the sync time when wal_sync_method is either open_datasync or open_sync. Waiting to create, drop or use a replication origin. Then identify which query See, One row per database, showing database-wide statistics about query cancels due to conflict with recovery on standby servers. The pg_stat_user_tables and pg_stat_sys_tables views contain the same information, but filtered to only show user and system tables respectively. disabled: This state is reported if track_activities is disabled in this backend. When using the cumulative statistics views and functions to monitor collected data, it is important to realize that the information does not update instantaneously. See, One row for each index in the current database, showing statistics about accesses to that specific index. Waiting to update limit on notification message storage. Waiting to acquire a lock on page of a relation. If the argument is NULL, reset statistics for all subscriptions. Indexes can be used by simple index scans, bitmap index scans, and the optimizer. Waiting to access the serializable transaction conflict SLRU cache. Time when this process was started. To reduce confusion for users expecting a different model of lag, the lag columns revert to NULL after a short time on a fully replayed idle system. Waiting for SLRU data to reach durable storage following a page write. Waiting to create or drop the tablespace. The idx_tup_read and idx_tup_fetch counts can be different even without any use of bitmap scans, because idx_tup_read counts index entries retrieved from the index while idx_tup_fetch counts live rows fetched from the table. - a BufFreeList LWLock was getting acquired to find a free buffer for a page - to change the association of buffer in buffer mapping hash table a LWLock is acquired on a hash partition to which the buffer to be associated belongs and as there were just 16 such partitions, there was huge contention when multiple clients Waiting to read or update information about serializable transactions. The server process is waiting for a timeout to expire. The IO:DataFileRead wait event occurs while data is Waiting for WAL from a stream at recovery. See, One row only, showing statistics about the WAL archiver process's activity. Waiting for background worker to start up. OID of the user logged into this WAL sender process, Name of the user logged into this WAL sender process, Name of the application that is connected to this WAL sender. Several predefined views, listed in Table28.1, are available to show the current state of the system. Waiting to read or update background worker state. See, One row only, showing statistics about the background writer process's activity. Waiting a new WAL segment created by copying an existing one to reach durable storage. Activity status of the WAL receiver process, First write-ahead log location used when WAL receiver is started, First timeline number used when WAL receiver is started. Waiting for parallel query dynamic shared memory allocation. The LWLock:BufferIO event occurs when Aurora PostgreSQL or RDS for PostgreSQL is waiting for other processes to finish their input/output (I/O) operations when concurrently trying to access a page. Waiting for a write when creating a new WAL segment by copying an existing one. The functions for per-function statistics take a function OID. Waiting for activity from child process when executing. My application is using Postgres as DBMS, the version of Postgres that i'm using is 10.3 with the extension Postgis installed. This has no effect in a quorum-based synchronous replication. See, One row per WAL sender process, showing statistics about replication to that sender's connected standby server. Waiting to fill a dynamic shared memory backing file with zeroes. PostgreSQL also supports reporting dynamic information about exactly what is going on in the system right now, such as the exact command currently being executed by other server processes, and which other connections exist in the system. LWLock:buffer_mapping. Waiting to elect a Parallel Hash participant to allocate a hash table. This can be used to gauge the delay that, Time elapsed between flushing recent WAL locally and receiving notification that this standby server has written and flushed it (but not yet applied it). Time spent reading data file blocks by backends in this database, in milliseconds (if track_io_timing is enabled, otherwise zero), Time spent writing data file blocks by backends in this database, in milliseconds (if track_io_timing is enabled, otherwise zero), Time spent by database sessions in this database, in milliseconds (note that statistics are only updated when the state of a session changes, so if sessions have been idle for a long time, this idle time won't be included), Time spent executing SQL statements in this database, in milliseconds (this corresponds to the states active and fastpath function call in pg_stat_activity), idle_in_transaction_time double precision, Time spent idling while in a transaction in this database, in milliseconds (this corresponds to the states idle in transaction and idle in transaction (aborted) in pg_stat_activity), Total number of sessions established to this database, Number of database sessions to this database that were terminated because connection to the client was lost, Number of database sessions to this database that were terminated by fatal errors, Number of database sessions to this database that were terminated by operator intervention. Waiting for a timeline history file received via streaming replication to reach durable storage. Waiting to replace a page in WAL buffers. The server process is waiting for activity on a socket connected to a user application. Waiting for a write of a WAL page during bootstrapping. The next use of statistical information will cause a new snapshot to be fetched. Priority of this standby server for being chosen as the synchronous standby in a priority-based synchronous replication. might be causing it. The server process is waiting for some interaction with another server process. Presently, the collector can count accesses to tables and indexes in both disk-block and individual-row terms. Waiting in main loop of logical replication apply process. Send time of last reply message received from standby server. This can be used to gauge the delay that. Possible values are: Activity status of the WAL receiver process, First write-ahead log location used when WAL receiver is started, First timeline number used when WAL receiver is started, Last write-ahead log location already received and flushed to disk, the initial value of this field being the first log location used when WAL receiver is started, Timeline number of last write-ahead log location received and flushed to disk, the initial value of this field being the timeline number of the first log location used when WAL receiver is started, Send time of last message received from origin WAL sender, Receipt time of last message received from origin WAL sender, Last write-ahead log location reported to origin WAL sender, Time of last write-ahead log location reported to origin WAL sender, Replication slot name used by this WAL receiver. Wait Events of Type BufferPin, Table28.8. Waiting to access the shared per-process data structures (typically, to get a snapshot or report a session's transaction ID). Waiting in background writer process, hibernating. This can be used to gauge the delay that synchronous_commit level remote_write incurred while committing if this server was configured as a synchronous standby. Increase the number of wal_buffers available to the database. Waiting for a read during reorder buffer management. wait_event will identify the specific wait point. Per-Backend Statistics Functions, pg_stat_get_backend_idset () setof integer. Waiting to read or update the state of prepared transactions. The pg_stat_activity view will have one row per server process, showing information related to the current activity of that process. Waiting to associate a data block with a buffer in the buffer pool. All temporary files are counted, regardless of why the temporary file was created, and regardless of the, Number of deadlocks detected in this database, Time spent reading data file blocks by backends in this database, in milliseconds, Time spent writing data file blocks by backends in this database, in milliseconds, Number of queries in this database that have been canceled due to dropped tablespaces, Number of queries in this database that have been canceled due to lock timeouts, Number of queries in this database that have been canceled due to old snapshots, Number of queries in this database that have been canceled due to pinned buffers, Number of queries in this database that have been canceled due to deadlocks, Number of sequential scans initiated on this table, Number of live rows fetched by sequential scans, Number of index scans initiated on this table, Number of live rows fetched by index scans, Number of rows updated (includes HOT updated rows), Number of rows HOT updated (i.e., with no separate index update required), Estimated number of rows modified since this table was last analyzed, Last time at which this table was manually vacuumed (not counting, Last time at which this table was vacuumed by the autovacuum daemon, Last time at which this table was manually analyzed, Last time at which this table was analyzed by the autovacuum daemon, Number of times this table has been manually vacuumed (not counting, Number of times this table has been vacuumed by the autovacuum daemon, Number of times this table has been manually analyzed, Number of times this table has been analyzed by the autovacuum daemon, Number of index scans initiated on this index, Number of index entries returned by scans on this index, Number of live table rows fetched by simple index scans using this index, Number of disk blocks read from this table, Number of disk blocks read from all indexes on this table, Number of buffer hits in all indexes on this table, Number of disk blocks read from this table's TOAST table (if any), Number of buffer hits in this table's TOAST table (if any), Number of disk blocks read from this table's TOAST table indexes (if any), Number of buffer hits in this table's TOAST table indexes (if any), Number of disk blocks read from this index, Number of disk blocks read from this sequence, Number of times this function has been called, Total time spent in this function and all other functions called by it, in milliseconds, Total time spent in this function itself, not including other functions called by it, in milliseconds, Process ID of the server process handling the current session, Returns a record of information about the backend with the specified PID, or one record for each active backend in the system if, Returns the timestamp of the current statistics snapshot, Reset all statistics counters for the current database to zero (requires superuser privileges by default, but EXECUTE for this function can be granted to others. Waiting for I/O on a multixact_member buffer. Synchronous state of this standby server. Waiting for mapping data to reach durable storage during a logical rewrite. block. DN of the issuer of the client certificate, or NULL if no client certificate was supplied or if SSL is not in use on this connection. wait_event will identify the specific wait point. Priority of this standby server for being chosen as the synchronous standby in a priority-based synchronous replication. The pg_stat_activity view will have one row per server process, showing information related to the current activity of that process. buffer_io: Waiting for I/O on a data page. Such a system would show similar times while new WAL is being generated, but would differ when the sender becomes idle. Sometimes it may be more convenient to obtain just a subset of this information. Waiting to read data from the client while establishing a GSSAPI session. pg_stat_get_activity ( integer ) setof record. So the statistics will show static information as long as you continue the current transaction. Normally these parameters are set in postgresql.conf so that they apply to all server processes, but it is possible to turn them on or off in individual sessions using the SET command. Waiting for a buffered file to be truncated. Resets all statistics counters for the current database to zero. This event type indicates a process waiting for activity in its main processing loop. Pointers to free buffers and to the next victim are protected by one buffer strategy lock spinlock. Waiting to elect a Parallel Hash participant to allocate the initial hash table. Waiting for a timeline history file received via streaming replication to reach durable storage. purpose is for the same page to be read into the shared buffer. Waiting to read or update the replication progress. Alternatively, one can build custom views using the underlying cumulative statistics functions, as discussed in Section28.2.24. buffer_mapping | DBmarlin Docs and Knowledge Base Waiting to allocate or free a replication slot. Waiting to read or write relation cache initialization file. Waiting for background worker to start up. pg_stat_get_backend_activity_start ( integer ) timestamp with time zone. LWLock:BufferIO - Amazon Aurora being read from storage. The argument can be one of CommitTs, MultiXactMember, MultiXactOffset, Notify, Serial, Subtrans, or Xact to reset the counters for only that entry. (Some locks have specific names; others are part of a group of locks each with a similar purpose.). Statistics Functions. Waiting to allocate or assign a transaction id. Additional functions related to the cumulative statistics system are listed in Table28.34. Lock: The backend is waiting for a heavyweight lock. The pg_stat_replication_slots view will contain one row per logical replication slot, showing statistics about its usage. If this field is null, it indicates either that the client is connected via a Unix socket on the server machine or that this is an internal process such as autovacuum. Waiting to read or update information about the state of synchronous replication. Waiting for a write while creating the data directory lock file. Waiting to read or update the progress of one replication origin. your workload peak time if you see LWLock:BufferIO coinciding with See Table28.4. Waiting for a replication slot control file to reach durable storage. Host name of the connected client, as reported by a reverse DNS lookup of, TCP port number that the client is using for communication with this backend, or. Monitoring systems should choose whether to represent this as missing data, zero or continue to display the last known value. The optimizer also accesses indexes to check for supplied constants whose values are outside the recorded range of the optimizer statistics because the optimizer statistics might be stale. Waiting to perform an operation on a list of locks held by serializable transactions. This is consistent with the goal of measuring synchronous commit and transaction visibility delays for recent write transactions. The next use of statistical information will (when in snapshot mode) cause a new snapshot to be built or (when in cache mode) accessed statistics to be cached. Waiting for SSL while attempting connection. Waiting to send bytes to a shared message queue. The function pg_stat_get_backend_idset provides a convenient way to generate one row for each active backend for invoking these functions. A process acquires an LWLock in a shared mode to read from the buffer and . Heavyweight locks, also known as lock manager locks or simply locks, primarily protect SQL-visible objects such as tables. Number of times transactions were spilled to disk while decoding changes from WAL for this slot. The server process is idle. Waiting to associate a data block with a buffer in the buffer pool. Resets statistics of the replication slot defined by the argument. Waiting for a serialized historical catalog snapshot to reach durable storage. Use partitioned tables (which also have partitioned indexes). Extensions can register their specific waits ( Extension ). The pg_stat_slru view will contain one row for each tracked SLRU cache, showing statistics about access to cached pages. A backend process wants to read a page into shared memory. If the standby server has entirely caught up with the sending server and there is no more WAL activity, the most recently measured lag times will continue to be displayed for a short time and then show NULL.