Update sys-server-file-audits-transact-sql.md

Added retention_days.

Update create-server-audit-transact-sql.md

Added retention period

Author: oberdansch

docs/relational-databases/system-catalog-views/sys-server-file-audits-transact-sql.md

@@ -42,7 +42,8 @@ dev_langs:
 |max_files|**int**|Maximum number of files to use without the rollover option.|  
 |reserved_disk_space|**int**|Amount of disk space to reserve per file.|  
 |log_file_path|**nvarchar(260)**|Path to where audit is located. File path for file audit, application log path for application log audit.|  
-|log_file_name|**nvarchar(260)**|Base name for the log file supplied in the CREATE AUDIT DDL. An incremental number is added to the base_log_name file as a suffix to create the log file name.|  
+|log_file_name|**nvarchar(260)**|Base name for the log file supplied in the CREATE AUDIT DDL. An incremental number is added to the base_log_name file as a suffix to create the log file name.|
+|retention_days|**int**|Lifetime in days of the audit log file. Applies to Azure SQL Database and Azure SQL Managed Instance <br /><br /> 0 = Unlimited. |  
 
 ## Permissions  
  Principals with the **ALTER ANY SERVER AUDIT** or **VIEW ANY DEFINITION** permission have access to this catalog view. In addition, the principal must not be denied **VIEW ANY DEFINITION** permission.  

docs/t-sql/statements/create-server-audit-transact-sql.md

@@ -55,6 +55,7 @@ CREATE SERVER AUDIT audit_name
     [ , ON_FAILURE = { CONTINUE | SHUTDOWN | FAIL_OPERATION } ]
     [ , AUDIT_GUID = uniqueidentifier ]
     [ , OPERATOR_AUDIT = { ON | OFF } ]
+    [ , RETENTION_DAYS = integer ]
 }
 
 <predicate_expression> ::=
@@ -141,6 +142,12 @@ To support scenarios such as database mirroring or databases participating in an
 
 Indicates whether auditing captures Microsoft support engineer operations when they need to access your server during a support request.
 
+#### RETENTION_DAYS 
+
+**Applies to:** Azure SQL Managed Instance and Azure SQL Database only.
+
+Indicates the number of days of the audit log file storage period.
+
 #### predicate_expression
 
 Specifies the predicate expression used to determine if an event should be processed or not. Predicate expressions are limited to a length of 3,000 characters, which limits string arguments.