How snapshot is handel at the time of database recover.

hi, (sqlserver 2008r2)
   in following link
https://technet.microsoft.com/en-us/library/ms173763(v=sql.105).aspx
in SNAPSHOT para
"Except
when a database is being recovered, SNAPSHOT transactions do not request locks when reading data. SNAPSHOT transactions reading data do not block other transactions from writing data. Transactions writing data do not block SNAPSHOT transactions from reading
data."
1) please tel me how it handels  snapshot transactions in database recovery ?
2) In how many cases database goes in recover and how often?
3) This is from the above link please tel me if have under stood correctlly
"When the snapshot isolation level is enabled, if you are deleting a row on a heap (a table without clustered index) and the transaction
log fills before the log record for ghost row is persisted, the database is taken offline. If this occurs, the database will automatically restart, undergo a full recovery, and come online."
my question is by saying "When the snaphot isolation level is enabled" that means when
"ALLOW_SNAPSHOT_ISOLATION " Command is used to enable snapshot in database not the setting of snapshot isolation
in any query so that one can start  transaction?
yours
sincerly

Hi,
The snapshot option is similar to the serializable isolation level. Therefore the reading data is always the last committed version of the row as this isolation level uses row versioning instead of shared locks. 
1) this transaction relies on row versioning and is visible after you have committed it.
2)When using the syntax " ALTER DATABASE DBNAME SET ALLOW_SNAPSHOT_ISOLATION ON;", you will enable snapshot for the entire database.
3)What I understand is that when you delete a row and this transaction is not committed it will not be visible for the reader, because reading data is only possible of the last committed version as snapshot is based on row versioning.
Hopefully this answers you question. 
If this answers your question please propos it as an answer.
Reshma

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