solidDB Help : Programming : Using HotStandby with applications : Transparent Connectivity : Failure transparency in Transparent Connectivity
  
Failure transparency in Transparent Connectivity
Failure transparency handles the masking of failures.
When a connection switch is executed by the driver, some of the session context can be lost and the application must reconstruct it. The amount of the preserved state is dictated by the Transparent Failover (TF) level.
Note that, regardless of the TF level, the following situations apply when a failover happens:
The updates of the current transactions are lost (because of the transaction rollback).
Open cursors and their positions are lost.
The TF level is set with the TF_LEVEL attribute for an ODBC connection, see Transparent Connectivity with ODBC, or with the non-standard property solid_tf_level for a JDBC connection, see Transparent Connectivity with JDBC.
The following TF levels can be configured:
NONE: failure transparency is disabled (default).
CONNECTION: no state is preserved, that is, it is unnecessary to reconnect in the case of failover or switchover.
SESSION: most of the session state is preserved. The preservation of the session state is implemented by caching the necessary data in the driver. The higher transparency level is achieved at the expense of the response time of the requests that require caching, as well as increased memory usage in the driver.
The states of prepared statements are preserved.
The effects of the following statements are preserved:
SET CATALOG
SET SQL INFO
SET SQL SORTARRAYSIZE
SET SQL CONVERTORSTOUNIONS
SET SQL JOINPATHSPAN
SET LOCK TIMEOUT
SET IDLE TIMEOUT
SET OPTIMISTIC LOCK TIMEOUT
SET STATEMENT MAXTIME
SET ISOLATION LEVEL
SET DURABILITY
SET SAFENESS
SET SCHEMA
SET SYNC USER
SET SYNC MODE
The following standard ODBC attributes are preserved:
SQL_ATTR_ACCESS_MODE (SET READ ONLY, SET READ WRITE)
SQL_ATTR_CURRENT_CATALOG (duplicates SET CATALOG)
SQL_ATTR_AUTOCOMMIT
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