PL/SQL User's Guide and Reference Release 8.1.6 Part Number A77069-01 |
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PL/SQL is designed primarily for high-speed transaction processing. That design imposes some program limits, which are discussed in this appendix.
PL/SQL is based on the programming language Ada. As a result, PL/SQL uses a variant of Descriptive Intermediate Attributed Notation for Ada (DIANA), which is a tree-structured intermediate language. It is defined using a meta-notation called Interface Definition Language (IDL). DIANA provides for communication internal to compilers and other tools.
At compile time, PL/SQL source code is translated into machine-readable m-code. Both the DIANA and m-code for a procedure or package are stored in the database. At run time, they are loaded into the shared (memory) pool. The DIANA is used to compile dependent procedures; the m-code is simply executed.
In the shared pool, a package spec, object type spec, stand-alone subprogram, or anonymous block is limited to 64K DIANA nodes. The nodes correspond to tokens such as identifiers, keywords, operators, and so on. The m-code is limited to 64K compiler-generated temporary variables.
Also, the PL/SQL compiler imposes various limits, some of which are given in Table E-1. Ordinarily, however, the DIANA size limit is exceeded before any of those limits.
To estimate how much memory a program unit requires, you can query the data dictionary view user_object_size
. The column parsed_size
returns the size (in bytes) of the "flattened" DIANA. In the following example, you get the parsed size of a package (displayed on the package spec line):
CREATE PACKAGE pkg1 AS PROCEDURE proc1; END pkg1; / CREATE PACKAGE BODY pkg1 AS PROCEDURE proc1 IS BEGIN NULL; END; END pkg1; / SQL> SELECT * FROM user_object_size WHERE name = 'PKG1'; NAME TYPE SOURCE_SIZE PARSED_SIZE CODE_SIZE ERROR_SIZE -------------------------------------------------------------------- PKG1 PACKAGE 46 165 119 0 PKG1 PACKAGE BODY 82 0 139 0
Unfortunately, you cannot estimate the number of DIANA nodes from the parsed size. Two program units with the same parsed size might require 1500 and 2000 DIANA nodes, respectively (because, for example, the second unit contains more complex SQL statements).
When a PL/SQL block, subprogram, package, or object type exceeds a size limit, you get an error such as program too large. Typically, this problem occurs with packages or anonymous blocks. With a package, the best solution is to divide it into smaller packages. With an anonymous block, the best solution is to redefine it as a group of subprograms, which can be stored in the database.
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