subquery and the main query are interdependent. To process each record in the subquery, it is necessary to fetch a record in the main query; i.e., the subquery fully depends on the main query. Sample predicate is TRUE if every value returned by the subquery satisfies the condition in the predicate of the main query. Chapter 4. Common Language Elements 77 Example Show only those clients whose ratings are TRUE if any of the values returned by the subquery satisfies the condition in the predicate of the main query. If the subquery would return no rows at all, the predicate is automatically considered as

otherwise, by default, it uses the same time zone as the operating system of the Firebird server process. This default can be overridden in firebird.conf, setting DefaultTimeZone.  Drivers may apply subquery and the main query are interdependent. To process each record in the subquery, it is necessary to fetch a record in the main query; i.e. the subquery fully depends on the main query. Sample Correlated predicate is TRUE if every value returned by the subquery satisfies the condition in the predicate of the main query. Example Show only those clients whose ratings are higher than the rating of every client

Windows and Linux. Creates a process for each client connec- tion, each with its own cache. Less re- source use if the number of connections is low. Single server process with a separate thread for each multi-processor Windows ma- chines, performance can even drop dramatically as the OS switches the process between CPUs. To prevent this, set the CPU_AFFINITY parameter in the configuration file ibconfig the install from a command shell or through a GUI interface. For Linux distributions that cannot process rpm programs, and for the various UNIX flavors, use the .tar.gz kit. You will find detailed instructions

You will notice, hopefully, that some commands do not give any printed output at all. gfix, in the main, only reports when problems are encountered. Always check the response code returned by gfix to be the users are able to continue processing data as normal and without loss. In the event that your main database file(s) become corrupted or unreadable, the DBA can activate Chapter 4. Shadow Files 7 the -⁠tw[o_phase] command. The command also takes the -⁠pr[ompt] option, as above, when used to process all transaction. The command line to carry out automatic two-phase recovery is: gfix -tw[o_phase]

databases.conf (Firebird 3.0 and higher) or aliases.conf (Firebird 2.5 and earlier) can be found in the main installation folder. By adding an entry to this folder, the full path to the database can be simplified who may want to connect at a later stage. By prepending the localhost: to the path, the server process, with Firebird running as user firebird, will create and own the file. To test the newly created documentation to set environmental variables. For the bash shell, the following example shows the process: $ export ISC_USER=sysdba $ export ISC_PASSWORD=secret $ /opt/firebird/bin/isql my_employee SQL>

undertaken in the creation of this document, but no Firebird databases were harmed during this process. All databases mentioned or described within this document are those with an ODS of 11.1 — in other file(s) — being part of the database — are also dropped! Shadow files are updated as the database main file(s) are updated and in this manner, the shadows are an identical copy of the database. In the 0x800 The database is still in backup mode, but changes are being merged from the diff file into the main pages. 0xC00 The current database state is unknown and changes need to be read from disk. hdr_shutdown_mask

(user) to access a Firebird database it must connect to the Firebird server process. On receiving a connect request the server process will authenticate the user credentials against the server users defined database require direct access to the database file itself. All access goes through the server process, which accesses the database file as needed to fulfil requests. It is the server that restricts from this description, Firebird security is predicated on the assumption that the Firebird server process will be running in an adequately secure environment. Firebird itself takes no precautions to provide

Superserver Processes Creates a separate process for every client connection, each with its own cache. Less resource use if the number of connections is low. A single process serves all connections, using threads connections grows. Permits fast, direct I/O to database files for local connections on Linux. The client process must have filesystem-level access rights to the database for this to work. On Linux, all local connections the server process needs access rights to the database file. Local connections On Windows, both architectures now support safe and reliable local connec- tions, with only the server process requiring

What are they? • Classic mode (aka MultiProcess) involves a single listening process that spawns off an additional process for each client connection. Using a locking mechanism, it allows shared connections connections to database files. • SuperClassic (ThreadedShared) is a single server process. Client connections are handled by separate threads, each having their own database page cache. Other processes database simultaneously (hence the Shared). • Superserver (ThreadedDedicated) is also a single server process with threads handling client connections. There is a single, common database page cache. The server

correct. Known Compatibility Issues 7 Important Such errors could also show up during the restore process when you are migrating databases to the new version. It will be necessary to correct these conditions a stub process named fb_inet_server.exe on Windows that listens for connection requests from network clients. On POSIX systems, the [x]inetd daemon performs this listening role. The stub process or daemon separate fb_inet_server process for each successful connection. Each process has its own private page cache and, on 32-bit systems, can use up to 2 GB of RAM. • Superserver is a process named fbserver.exe