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The sa_diagnostic_blocking table is owned by the dbo user, and records blocking events. If logging of blocking events is enabled, a row is inserted in this table each time a connection is blocked while trying to access a resource. Typically, this is caused by either a table or a row lock. A large number of blocks may indicate that you should examine the concurrency in your application to reduce contention for tables and rows.
There are two versions of this table: sa_diagnostic_blocking, and sa_tmp_diagnostic_blocking.
| Column name | Column type | Column constraint | Table constraints |
|---|---|---|---|
| logging_session_id | UNSIGNED INT | NOT NULL |
Foreign key references sa_diagnostic_cursor. Foreign key references sa_diagnostic_request. |
| lock_id | UNSIGNED BIGINT | NOT NULL | |
| request_id | UNSIGNED BIGINT |
Foreign key references sa_diagnostic_request. | |
| cursor_id | UNSIGNED BIGINT |
Foreign key references sa_diagnostic_cursor. | |
| original_table_object_id | UNSIGNED BIGINT | ||
| rowid | UNSIGNED BIGINT | ||
| block_time | TIMESTAMP | NOT NULL | |
| unblock_time | TIMESTAMP | ||
| blocked_by | UNSIGNED INT | NOT NULL |
logging_session_id A number uniquely identifying the logging session during which the diagnostic information was gathered.
lock_id The ID of the lock that caused the blocking if a row or table lock caused the block, otherwise NULL.
request_id The ID of the request that was blocked if the block did not occur because of a cursor, otherwise NULL. This value corresponds to the ID assigned to the request in sa_diagnostic_request.
cursor_id The ID of the cursor if the block occurred because of a cursor, otherwise NULL. This value corresponds to the ID assigned to the cursor in sa_diagnostic_cursor.
original_table_object_id If the block occurred because of a table lock, the ID of the table on which the block occurred, otherwise NULL.
rowid If the block occurred because of a row lock, the ID of the row on which the block occurred, otherwise NULL.
block_time The time at which the block occurred.
unblock_time The time at which the block ended.
blocked_by The ID of the connection that held the lock, causing the block.