Catalog Concatenation

Definitions

You can logically combine two or more SAS catalogs by concatenating them. This allows you to access the contents of several catalogs, using one catalog name . There are two types of concatenation, explicit and implicit .

Implicit catalog concatenation

• results from a concatenation of libraries through a LIBNAME statement. When two or more libraries are logically combined through concatenation, any catalogs with the same name in each library become logically combined as well.

Explicit catalog concatenation

• is a concatenation that is specified by the global CATNAME statement in which the catalogs to be concatenated are specifically (or explicitly) named. During explicit catalog concatenation, the CATNAME statement sets up a logical catalog in memory.

Example 1: Implicit Concatenation

This LIBNAME statement concatenates the two SAS data libraries:

 libname both ('  SAS-data-library 1  ''  SAS-data-library 2  '); 

Members of library1	Members of library2
MYCAT.CATALOG	MYCAT.CATALOG
TABLE1.DATA	MYCAT2.CATALOG
TABLE3.DATA	TABLE1.DATA
	TABLE1.INDEX
	TABLE2.DATA
	TABLE2.INDEX

The concatenated libref BOTH would have the following:

Concatenated libref BOTH

MYCAT.CATALOG (from path 1 and 2)

MYCAT2.CATALOG (from path 2)

TABLE1.DATA (from path 1)

TABLE2.DATA (from path 2)

TABLE2.INDEX (from path 2)

TABLE3.DATA (from path 1)

Notice that TABLE1.INDEX does not appear in the concatenation but TABLE2.INDEX does appear. SAS suppresses listing the index when its associated data file is not part of the concatenation.

So what happened to the catalogs when the libraries were concatenated? A resulting catalog now exists logically in memory, with the full name BOTH.MYCAT.CATALOG. This catalog combines each of the two physical catalogs residing in 'library 1' and 'library2', called MYCAT.CATALOG.

To understand the contents of the concatenation BOTH.MYCAT, first look at the contents of both parts of the concatenation. Assume that the two original MYCAT.CATALOG files contain the following:

Contents of MYCAT.CATALOG in library1	Contents of MYCAT.CATALOG in library 2
A.FRAME	A.GRSEG
C.FRAME	B.FRAME
	C.FRAME

Then the combined catalog BOTH.MYCAT contains the following:

BOTH.MYCAT

A.GRSEG (from path 2)

A.FRAME (from path 1)

B.FRAME (from path 2)

C.FRAME (from path 1)

Example 2: Explicit Concatenation

The syntax of the CATNAME statement is:

 CATNAME libref.catref            (libref-1.catalog-1 (ACCESS=READONLY)             libref-n.catalog-n (ACCESS=READONLY)); 

To disassociate a concatenated catalog the syntax is:

 CATNAME libref.catref  _ALL_ clear; 

In the following example, there must be a libref that is defined and named CATDOG. The libref CATDOG establishes the scope for the explicit concatenation definition.

Note: If a file in CATDOG named COMBINED.CATALOG already exists, it becomes inaccessible until the explicit concatenation CATDOG.COMBINED is cleared.

Members of library1	Members of library2
MYCAT.CATALOG	MYDOG.CATALOG
TABLE1.DATA	MYCAT2.CATALOG
TABLE3.DATA	TABLE1.DATA
	TABLE1.INDEX
	TABLE2.DATA
	TABLE2.INDEX

If we issue the following statement,

 CATNAME catdog.combined            (library1.mycat (ACCESS=READONLY)             library2.mydog (ACCESS=READONLY)); 

then the concatenated catalog CATDOG.COMBINED combines the following catalogs:

Concatenated catalog CATALOG.COMBINED

MYCAT.CATALOG (from library 1)

MYDOG.CATALOG (from library 2)

Note: In explicit concatenation only the named catalogs are combined. In implicit concatenation, any catalogs that have the same name in their respective libraries are concatenated when those libraries are concatenated.

The previous CATNAME statement creates a catalog that exists logically in memory. This catalog, named CATDOG.COMBINED.CATALOG, combines the two physical catalogs residing in library1 and library2, called MYCAT.CATALOG and MYDOG.CATALOG respectively.

To understand the contents of the concatenation COMBINED.CATALOG, first look at the contents of both parts of the concatenation. The two original catalog files contain the following entries:

MYCAT.CATALOG library 1	MYDOG.CATALOG library 2
A.FRAME	A.GRSEG
C.FRAME	B.FRAME
	C.FRAME

The concatenated catalog COMBINED contains:

COMBINED.CATALOG contents

A.GRSEG (from MYDOG)

A.FRAME (from MYCAT)

B.FRAME (from MYDOG)

C.FRAME (from MYCAT)

Rules for Catalog Concatenation

The rules for catalog concatenation are the same, whether the catalogs are implicitly or explicitly concatenated.

• When a catalog entry is open for input or update, the parts are searched and the first occurrence of the specified entry is used.

• When an item is open for output, it will be created in the catalog that is listed first in the concatenation.

  Note: A new catalog entry is created in the first catalog even if there is an item with the same name in another part of the concatenation.

  Note: If the first catalog in a concatenation that is opened for update does not exist, the item will be written to the next catalog that exists in the concatenation.

• When you want to delete or rename a catalog entry, only the first occurrence of the entry is affected.

• Any time a list of catalog entries is displayed, only one occurrence of the catalog entry is shown.

  Note: Even if a catalog entry occurs multiple times in the concatenation, only the first occurrence is shown.