|Oracle® Database PL/SQL Language Reference
11g Release 2 (11.2)
Part Number E17126-03
Package Treated as Stateless if State is Constant for Life of Session
Before Release 188.8.131.52, if a session recompiled the body of a stateful package, and then another session that had instantiated that package referenced it, the latter session got the severely disruptive error ORA-04068 (“existing state of packages … has been discarded”). Therefore, "hot patching" packages was likely to disrupt their users.
As of Release 184.108.40.206, Oracle Database treats a package as stateless if its state is constant for the life of a session (or longer). This is the case for a package whose items are all compile-time constants. Therefore, "hot patching" packages (especially noneditioned packages) is much less likely to disrupt sessions that are using them.
For more information, see "Package State".
The PL/SQL features for Oracle Database 11g Release 2 (220.127.116.11) are:
DBMS_PARALLEL_EXECUTE package enables you to incrementally update the data in a large table in parallel, in two high-level steps:
Group sets of rows in the table into smaller chunks.
Apply the desired
UPDATE statement to the chunks in parallel, committing each time you have finished processing a chunk.
Oracle recommends this technique whenever you are updating a lot of data. It improves performance, reduces rollback space consumption, and reduces the number of row locks held.
For more information, see "Updating Large Tables in Parallel".
FORCE Option in CREATE TYPE Statement
Before Release 11.2, if a
TYPE statement specified an existing type that had either type dependents or table dependents, the statement failed with error ORA-02303. As of Release 11.2, if you specify
FORCE in this situation, the statement fails only if the existing type has table dependents, not if it has type dependents.
For more information, see "CREATE TYPE Statement".
Crossedition triggers are intended to fire when database manipulation language (DML) statements change database tables while an online application that uses the tables is being patched or upgraded with edition-based redefinition. The body of a crossedition trigger is designed to handle these changes so that they can be appropriately applied after the changes to the application code are completed.
For more information, see "CREATE TRIGGER Statement".
See Also:Oracle Database Advanced Application Developer's Guide for information about edition-based redefinition in general and crossedition triggers in particular, including the relationship between crossedition triggers and editions
ALTER TYPE Statement Restrictions for Editioned ADTs
If you use edition-based redefinition to patch or upgrade an application, you use editioned objects. If any of your editioned objects are Abstract Data Types (ADTs), see "Restriction on type".
See Also:Oracle Database Advanced Application Developer's Guide for information about edition-based redefinition in general and editioned objects in particular
RESET option for ALTER TYPE Statement
RESET option of the
TYPE statement resets the version of a type to 1, so that it is no longer considered to be evolved.
RESET is intended for evolved ADTs that are preventing their owners from being editions-enabled. For more information, see "ALTER TYPE Statement".
See Also:Oracle Database Advanced Application Developer's Guide for information about enabling editions for users
Automatic Detection of Data Sources of Result-Cached Function
Before Release 11.2, you had to specify any data sources on which a result-cached function depended.
As of Release 11.2, Oracle Database automatically detects all data sources that are queried while a result-cached function is running.
For more information, see "PL/SQL Function Result Cache".
Result Caches in Oracle RAC Environment Are No Longer Private
For Oracle Database 11g Release 1 (11.1), each database instance in an Oracle RAC environment had a private function result cache, available only to sessions on that instance. If a required result was missing from the private cache of the local instance, the body of the function ran to compute the result, which was then added to the local cache. The result was not retrieved from the private cache of another instance.
For Release 11.2, each database instance manages its own local result cache, but the local result cache is no longer private—sessions attached to remote database instances can access its contents. If a required result is missing from the result cache of the local instance, the result might be retrieved from the local cache of another instance, instead of being locally computed.
For more information, see "Result Caches in Oracle RAC Environment".
The PL/SQL features for Release 11.1 are:
Enhancements to Regular Expression Built-In SQL Functions
The regular expression built-in SQL functions
REGEXP_SUBSTR have increased functionality. A new regular expression built-in function,
REGEXP_COUNT, returns the number of times a pattern appears in a string. These functions act the same in SQL and PL/SQL.
Oracle Database Advanced Application Developer's Guide for information about the implementation of regular expressions
SIMPLE_INTEGER, SIMPLE_FLOAT, and SIMPLE_DOUBLE Data Types
SIMPLE_DOUBLE data types are predefined subtypes of
BINARY_DOUBLE, respectively. Each subtype has the same range as its base type and has a
SIMPLE_INTEGER differs significantly from
PLS_INTEGER in its overflow semantics, but
SIMPLE_DOUBLE are identical to their base types, except for their
You can use
SIMPLE_INTEGER when the value will never be
NULL and overflow checking is unnecessary. You can use
SIMPLE_DOUBLE when the value will never be
NULL. Without the overhead of checking for nullness and overflow, these subtypes provide significantly better performance than their base types when
PLSQL_CODE_TYPE='NATIVE', because arithmetic operations on
SIMPLE_INTEGER values are done directly in the hardware. When
PLSQL_CODE_TYPE='INTERPRETED', the performance improvement is smaller.
For more information, see:
CONTINUE statement exits the current iteration of a loop and transfers control to the next iteration (in contrast with the
EXIT statement, which exits a loop and transfers control to the end of the loop). The
CONTINUE statement has two forms: the unconditional
CONTINUE and the conditional
For more information, see:
Sequences in PL/SQL Expressions
NEXTVAL make writing PL/SQL source code easier for you and improve run-time performance and scalability. You can use
NEXTVAL wherever you can use a
For more information, see "CURRVAL and NEXTVAL in PL/SQL".
Dynamic SQL Enhancements
Both native dynamic SQL and the
DBMS_SQL package have been enhanced.
All data types that native dynamic SQL supports are supported.
DBMS_SQL.PARSE function accepts a
CLOB argument, allowing dynamic SQL statements larger than 32 KB.
The new "DBMS_SQL.TO_REFCURSOR Function" enables you to switch from the
DBMS_SQL package to native dynamic SQL.
The new "DBMS_SQL.TO_CURSOR_NUMBER Function" enables you to switch from native dynamic SQL to the
Named and Mixed Notation in PL/SQL Subprogram Invocations
Before Release 11.1, a SQL statement that invoked a PL/SQL subprogram had to specify the actual parameters in positional notation. As of Release 11.1, named and mixed notation are also allowed. This improves usability when a SQL statement invokes a PL/SQL subprogram that has many defaulted parameters, and few of the actual parameters must differ from their default values.
For an example, see the
SELECT statements in Example 8-21.
PL/SQL Function Result Cache
A function result cache can save significant space and time. Each time a result-cached function is invoked with different parameter values, those parameters and their result are stored in the cache. Subsequently, when the same function is invoked with the same parameter values, the result is retrieved from the cache, instead of being recomputed.
Before Release 11.1, if you wanted your PL/SQL application to cache the results of a function, you had to design and code the cache and cache-management subprograms. If multiple sessions ran your application, each session had to have its own copy of the cache and cache-management subprograms. Sometimes each session had to perform the same expensive computations.
As of Release 11.1, PL/SQL provides a function result cache. To use it, use the
RESULT_CACHE clause in each PL/SQL function whose results you want cached. Because the function result cache resides in a shared global area (SGA), it is available to any session that runs your application.
After you convert your application to PL/SQL function result caching, it uses more SGA, but significantly less total system memory.
For more information, see:
Compound DML Triggers
A compound DML trigger created on a table or editioning view can fire at multiple timing points. Each timing point section has its own executable part and optional exception-handling part, but all of these parts can access a common PL/SQL state. The common state arises when the triggering statement starts and disappears when the triggering statement completes, even when the triggering statement causes an error.
Before Release 11.1, application developers modeled the common state with an ancillary package. This approach was both cumbersome to program and subject to memory leak when the triggering statement caused an error and the after-statement trigger did not fire. Compound triggers help program an approach where you want the actions you implement for the various timing points to share common data.
For more information, see "Compound DML Triggers".
More Control Over Triggers
The SQL statement
TRIGGER now supports
FOLLOWS clauses that give you more control over triggers. The
DISABLE clause lets you create a trigger in the disabled state, so that you can ensure that your code compiles successfully before you enable the trigger. The
ENABLE clause explicitly specifies the default state. The
FOLLOWS clause lets you control the firing order of triggers that are defined on the same table and have the same timing point.
For more information, see:
Automatic Subprogram Inlining
Subprogram inlining replaces a subprogram invocation (to a subprogram in the same PL/SQL unit) with a copy of the invoked subprogram, which almost always improves program performance.
You can use
PRAGMA INLINE to specify that individual subprogram invocations are, or are not, to be inlined. You can also turn on automatic inlining—that is, ask the compiler to search for inlining opportunities—by setting the compilation parameter
PLSQL_OPTIMIZE_LEVEL to 3 (the default is 2).
In the rare cases when automatic inlining does not improve program performance, you can use the PL/SQL hierarchical profiler to identify subprograms for which you want to turn off inlining.
For more information, see:
See Also:Oracle Database Reference for information about the compilation parameter
PL/Scope is a compiler-driven tool that collects and organizes data about user-defined identifiers from PL/SQL source code. Because PL/Scope is a compiler-driven tool, you use it through interactive development environments (such as SQL Developer and JDeveloper), rather than directly.
PL/Scope enables the development of powerful and effective PL/Scope source code browsers that increase PL/SQL developer productivity by minimizing time spent browsing and understanding source code.
For more information, see "Collecting Data About User-Defined Identifiers".
PL/SQL Hierarchical Profiler
The PL/SQL hierarchical profiler reports the dynamic execution profile of your PL/SQL program, organized by subprogram invocations. It accounts for SQL and PL/SQL execution times separately. Each subprogram-level summary in the dynamic execution profile includes information such as number of invocations to the subprogram, time spent in the subprogram itself, time spent in the subprogram's subtree (that is, in its descendent subprograms), and detailed parent-children information.
You can browse the generated HTML reports in any browser. The browser's navigational capabilities, combined with well chosen links, provide a powerful way to analyze performance of large applications, improve application performance, and lower development costs.
For more information, see "Profiling and Tracing PL/SQL Programs".
PL/SQL Native Compiler Generates Native Code Directly
The PL/SQL native compiler now generates native code directly, instead of translating PL/SQL code to C code and having the C compiler generate the native code. An individual developer can now compile PL/SQL units for native execution without any set-up on the part of the DBA. Execution speed of natively compiled PL/SQL programs improves, in some cases by an order of magnitude.
For more information, see "Compiling PL/SQL Units for Native Execution".