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Oracle® Database Reference
11g Release 2 (11.2)

E40402-14
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V$XSTREAM_APPLY_READER

V$XSTREAM_APPLY_READER displays information about each XStream apply reader. The apply reader is a process which reads (dequeues) messages from the queue, computes message dependencies, and builds transactions. It passes the transactions on to the coordinator in commit order for assignment to the apply servers. An apply reader is a subcomponent of an apply process, outbound server, or inbound server.

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
STATE VARCHAR2(74) Shows the state of the apply reader and the hash server. The possible values include:
  • INITIALIZING - Starting up

  • IDLE - Performing no work

  • DEQUEUE MESSAGES - Dequeuing messages from the queue

  • SCHEDULE MESSAGES - Computing dependencies between messages and assembling messages into transactions

  • SPILLING - Spilling unapplied messages from memory to hard disk

  • PAUSED - WAITING FOR DDL TO COMPLETE - Waiting for a data definition language (DDL) logical change record (LCR) to be applied

The state of the apply reader is displayed first, followed by the state of the hash server. A semicolon separates the apply reader state from the hash server state.

TOTAL_MESSAGES_DEQUEUED NUMBER Total number of messages dequeued since the apply process was last started
TOTAL_MESSAGES_SPILLED NUMBER 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 Elapsed time (in hundredths of a second) spent spilling messages since the apply process was last started
OLDEST_SCN_NUM NUMBER Oldest SCN
OLDEST_XIDUSN NUMBER Transaction ID undo segment number of the oldest transaction that either has been applied or is being applied
OLDEST_XIDSLT NUMBER Transaction ID slot number of the oldest transaction that either has been applied or is being applied
OLDEST_XIDSQN NUMBER Transaction ID sequence number of the oldest transaction that either has been applied or is being applied
SPILL_LWM_SCN NUMBER Spill low-watermark SCN
PROXY_SID NUMBER When the apply process uses combined capture and apply, the session ID of the propagation receiver that is responsible for direct communication between capture and apply. If the apply process does not use combined capture and apply, then this column is 0.
PROXY_SERIAL NUMBER When the apply process uses combined capture and apply, the serial number of the propagation receiver that is responsible for direct communication between capture and apply. If the apply process does not use combined capture and apply, then this column is 0.
PROXY_SPID VARCHAR2(12) When the apply process uses combined capture and apply, the process identification number of the propagation receiver that is responsible for direct communication between capture and apply. If the apply process does not use combined capture and apply, then this column is 0.
BYTES_RECEIVED NUMBER When the apply process uses combined capture and apply, the number of bytes received by the apply process from the capture process since the apply process last started. If the apply process does not use combined capture and apply, then this column is not populated.
DEQUEUED_POSITION RAW(64) Dequeued position. This column is populated only for an apply process that is functioning as an XStream inbound server.
SPILL_LWM_POSITION RAW(64) Spill low-watermark position. This column is populated only for an apply process that is functioning as an XStream inbound server.
OLDEST_TRANSACTION_ID VARCHAR2(128) Oldest transaction ID
TOTAL_LCRS_WITH_DEP NUMBER Total number of LCRs with row-level dependencies since the apply process last started
TOTAL_LCRS_WITH_WMDEP NUMBER Total number of LCRs with watermark dependencies since the apply process last started.

A watermark dependency occurs when an apply process must wait until the apply process's low watermark reaches a particular threshold.

TOTAL_IN_MEMORY_LCRS NUMBER Total number of LCRs currently in memory
SGA_ALLOCATED NUMBER The total amount of shared memory (in bytes) allocated from the XStreams pool for the apply process since the apply process last started

Note:

This view is available starting with Oracle Database 11g Release 2 (11.2.0.4).

Note:

The ELAPSED_SCHEDULE_TIME column is 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.