V$STREAMS_APPLY_READER

V$STREAMS_APPLY_READER displays information about each apply reader. The apply reader for an apply process is a process which reads (dequeues) messages from the queue, computes message dependencies, builds transactions, and passes the transactions on to the apply process coordinator in commit order for assignment to the apply servers.

Column	Datatype	Description
`SID`	`NUMBER`	Session ID of the reader's session
`SERIAL#`	`NUMBER`	Serial number of the reader's session
`APPLY#`	`NUMBER`	Apply process number. An apply process is an Oracle background process, prefixed by `ap`.
`APPLY_NAME`	`VARCHAR2(30)`	Name of the apply process that spilled one or more transactions
`STATE`	`VARCHAR2(17)`	State of the reader: `INITIALIZING` - Starting up `IDLE` - Performing no work `DEQUEUE MESSAGES` - Dequeueing messages from the apply process queue `SCHEDULE MESSAGES` - Computing dependencies between messages and assembling messages into transactions `SPILLING` - Spilling unapplied messages from memory to hard disk `PAUSED` - Waiting for a DDL LCR to be applied
`TOTAL_MESSAGES_DEQUEUED`	`NUMBER`	Total number of messages dequeued since the apply process was last started.
`TOTAL_MESSAGES_SPILLED`	`NUMBER`	The number of messages spilled by the reader since the apply process was last started.
`DEQUEUE_TIME`	`DATE`	Time when the last message was received
`DEQUEUED_MESSAGE_NUMBER`	`NUMBER`	Number of the last message received
`DEQUEUED_MESSAGE_CREATE_TIME`	`DATE`	For captured messages, creation time at the source database of the last message received. For user-enqueued messages, time when the message was enqueued into the queue at the local database.
`SGA_USED`	`NUMBER`	Amount (in bytes) of SGA memory used by the apply process since it was last started
`ELAPSED_DEQUEUE_TIME`	`NUMBER`	Time elapsed (in hundredths of a second) dequeuing messages since the apply process was last started
`ELAPSED_SCHEDULE_TIME`	`NUMBER`	Time elapsed (in hundredths of a second) scheduling messages since the apply process was last started. Scheduling includes computing dependencies between messages and assembling messages into transactions.
`ELAPSED_SPILL_TIME`	`NUMBER`	The elapsed time spent spilling messages, in centiseconds, since the apply process was last started.
`LAST_BROWSE_NUM`	`NUMBER`	Last browse SCN
`OLDEST_SCN_NUM`	`NUMBER`	Oldest SCN
`LAST_BROWSE_SEQ`	`NUMBER`	Last browse sequence number
`LAST_DEQ_SEQ`	`NUMBER`	Last dequeue sequence number
`OLDEST_XIDUSN`	`NUMBER`	Transaction ID undo segment number of the oldest transaction to be applied/being applied
`OLDEST_XIDSLT`	`NUMBER`	Transaction ID slot number of the oldest transaction to be applied/being applied
`OLDEST_XIDSQN`	`NUMBER`	Transaction ID sequence number of the oldest transaction to be applied/ being applied

Note:

The ELAPSED_DEQUEUE_TIME and ELAPSED_SCHEDULE_TIME columns are only populated if the TIMED_STATISTICS initialization parameter is set to true, or if the STATISTICS_LEVEL initialization parameter is set to TYPICAL or ALL.