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Runtime Configuration

The behaviour of these functions is affected by settings in php.ini.

Here's a short explanation of the configuration directives.

oci8.connection_class string

This user defined text is used by Oracle 11g Database Resident Connection Pooling (DRCP) connections to sub-partition the connection pool. It allows OCI8 persistent connections from an application to reuse database sessions from a previous PHP script, giving better scalability. When an application uses a database pooled process previously used with a different connection class, the session settings such as the default Oracle date format are reset. This prevents accidental sharing of information between different applications.

The value can be set at runtime with ini_set() prior to connecting.

To use DRCP, OCI8 must be linked with Oracle 11g libraries and the database must be Oracle 11g. The connection pool must be enabled in the database, the oci8.connection_class should be set to the same string for all web servers running the same application, and the OCI8 connection string must specify to use a pooled server.

oci8.default_prefetch int

This option sets the default number of extra rows that will be fetched and cached automatically whenever a low-level request for data from the database is made. Setting a value of 0 turns off prefetching.

The prefetch value does not alter the number of rows that functions like oci_fetch_array() return to the user; the prefetching and caching of rows is handled internally in OCI8.

The value can be set per-statement with oci_set_prefetch() prior to statement execution.

In PHP 5.3 (PECL OCI8 1.3.4) the default value was increased from 10 to 100.

In PHP 5.3.2 (PECL OCI8 1.4) the minimum value settable was reduced from 1 to 0, allowing prefetching to be turned off.

When using Oracle Database 12c or later, the prefetch value set by PHP can be overridden by Oracle's client oraaccess.xml configuration file. Refer to Oracle documentation for more detail.

Note: A larger prefetch can result in improved performance, at the cost of some increased memory usage. For queries that return large amounts of data, the performance benefit can be significant.

oci8.events boolean

Using On allows PHP to be notified of database Fast Application Notification (FAN) events.

Without FAN, when a database instance or machine node fails unexpectedly, PHP applications may be blocked waiting for a database response until a TCP timeout expires. With FAN events, PHP applications are quickly notified of failures that affect their established database connections. The OCI8 extension will clean up unusable connections in the persistent connection cache.

When using On, the database must also be configured to post FAN events.

FAN support is available when OCI8 is linked with Oracle 10gR2 (or later) libraries and connected to Oracle Database 10gR2 (or later).

oci8.max_persistent int

The maximum number of persistent OCI8 connections per PHP process. Setting this option to -1 means that there is no limit.

oci8.old_oci_close_semantics boolean

This option controls oci_close() behaviour. Enabling it means that oci_close() will do nothing; the connection will not be closed until the end of the script. This is for backward compatibility only. If you find that you need to enable this setting, you are strongly encouraged to adjust the oci_close() calls in your application instead of enabling this option.

oci8.persistent_timeout int

The maximum number of seconds that a PHP process is allowed to keep an idle persistent connection open. Setting this option to -1 means that idle persistent connections will be retained until the PHP process terminates or the connection is explicitly closed with oci_close().

Note: In PHP, the expiry of idle resources is not alarm-based. It occurs when PHP finishes processing a script and checks the last-used timestamp of resources. Hence there is a paradox that idle connections can only be closed when there is some activity (though not necessarily OCI8 related) in the PHP process. If there is more than one PHP process then each must individually be activated in order to trigger expiry of its idle resources. The introduction of Database Resident Connection Pooling (DRCP) in Oracle 11g resolves the memory and resource issues that oci8.max_persistent and oci8.persistent_timeout previously attempted to overcome.

Note: In PHP 5.3 (PECL OCI8 1.3), persistent connections can be closed with oci_close().

oci8.ping_interval int

The number of seconds that must pass before issuing a ping during oci_pconnect(). A ping ensures that the database connection is valid. When set to 0, persistent connections will be pinged every time oci_pconnect() is called. To disable pings completely, set this option to -1.

Note: Disabling pings allows oci_pconnect() to operate at the highest efficiency, but PHP may not be able to detect unusable connections, such as caused by network dropout, or if the Oracle database has gone down since PHP connected, until the connection is used later in the script. Consult the oci_pconnect() documentation for more information.

oci8.privileged_connect boolean

This option allows connections to use the privileged external credentials OCI_SYSOPER or OCI_SYSDBA.

Note: Seting this On can allow scripts on web servers running with the appropriate OS user privileges to connect as privileged database users without requiring a database password. This can be a security risk.

oci8.statement_cache_size int

This option enables statement caching, and specifies how many statements to cache. To disable statement caching just set this option to 0.

Statement caching removes the need to transmit the statement text to the database and removes the need to transmit any meta data about the statement back to PHP. This can significantly improve overall system performance in applications which reuse statements during the lifetime of a connection. Some extra database "cursors" may be held open under the assumption that statements will be reused.

Set this value to the size of the working set of statements used by your application. Setting too small a value can cause statements to be flushed from the cache before they are reused.

This option is of most use with persistent connections.

When using Oracle Database 12c, this value can be overridden and automatically tuned by Oracle's client oraaccess.xml file. Refer to Oracle documentation for more detail.