Shulou(Shulou.com)06/01 Report--

Other things you need to know.

The transaction log cannot be truncated during automatic seed setup

Automatic seed setting delaying log truncation. If the database load on the primary replica is high, a significant number of logs will be generated, and there may be a risk of filling up the log files. Of course, in most cases, the log file is set to grow automatically, there is no limit, and it is necessary to monitor the use of disk space where the log file is located during automatic seed setting.

The LOG_REUSE_WAIT_DESC column of the Sys.databases view reflects the reason for the delayed log truncation. However, when transaction truncation is delayed due to automatic seeding, the value of the LOG_REUSE_WAIT_DESC column is "NOTHING", which means that log truncation will not be prevented, and the log will actually be truncated when the log backup is performed, which is misleading.

Incorrect is_compression_enabled column values in sys.dm_hadr_physical_seeding_ stats table when compression is enabled

The Sys.dm_hadr_physical_seeding_stats view shows the status of the current automatic seed setting activity. The is_compression_enabled column of the view reflects the value when compression is started with or without compression using the trace flag 9567 in the automatic seed setting. Then, when compression is enabled, the value is 0, which is incorrect.

Delete all databases of the secondary copy before recreating the availability group set by the automatic seed

When recreating the availability group set by automatic seeding, if the database of the secondary copy is not deleted, the primary copy will first try to connect to the secondary copy. If the primary copy has not been restored and the log backup has not been made, the secondary copy will be connected, and the operation of synchronizing the primary copy will be completed automatically. If the primary copy has been restored or the log backup has been made, the secondary copy will not be connected. The test scenario is as follows:

The primary copy deletes the table, the secondary copy is connected to the secondary copy, and the delete operation is synchronized

Master copy delete table, backup log backup, secondary copy synchronization failed, query sys.dm_hadr_automatic_seeding, get 223 error: Database With Name Already Exists.

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