Quando a falha ocorre?

Serviço do SQL não inicia e no log do Windows, retorna erro : Passed to log scan in database 'master' is not valid. This error may indicate data corruption or that the log file (.ldf) does not match the data file (.mdf). If this error occurred during replication, re-create the publication. Otherwise, restore from backup if the problem results in a failure during startup. Cannot recover the master database. SQL Server is unable to run. Restore master from a full backup, repair it, or rebuild it. For more information about how to rebuild the master database, see SQL Server Books Online.

Como corrigir o erro?

Para corrigir, acesse a pasta de instalação da instância do SQL. (Poderá encontrar nos caminhos: C:\Program Files (x86)\Microsoft SQL Server ou C:\Program Files\Microsoft SQL Server)

Localize a pasta DATA - C:\Program Files (x86)\Microsoft SQL Server\MSSQL12.WOLTERSKLUWER\MSSQL\DATA

Renomeie os arquivos master.mdf e mastlog.ldf para master.mdf-old e masterlog.ldf-old.

 Acesse a pasta Template Data (C:\Program Files (x86)\Microsoft SQL Server\MSSQL12.WOLTERSKLUWER\MSSQL\Template Data) e copie os arquivos master.mdf e mastlog.ldf e cole na pasta DATA (C:\Program Files (x86)\Microsoft SQL Server\MSSQL12.WOLTERSKLUWER\MSSQL\DATA)

Acesse aos serviços do Windows, e inicie novamente o serviço do SQL Server da referida instância.