Endevor ELIB vs. PDSE usage

Products

• Endevor

Issue/Introduction

 What are the considerations for choosing between Endevor ELIB or PDSE?

Environment

All supported versions of Endevor

Resolution

Interestingly, ELIBs have some similarities to PDSEs. Both were introduced around 1990 and both were designed to avoid some limitations of PDSs, like these:

• No automatic space reuse, PDSs may need to be compressed
• Fixed size of directory, unable to expand
• Limited to 16 extents

 

And both have their advantages and both have their disadvantages.

 

ELIBs are Endevor proprietary data set format and can be used as Endevor base, delta and listing libraries.

 

Comparing PDSEs vs. ELIBs:

Advantages of PDSEs:

• Automatic space reuse and good fragmentation management
• Automatic directory expansion
• Can grow to 123 extents
• Universal compatibility. All common tools can work with PDSE members.
• The performance is roughly comparable to ELIBs, except in high concurrent update scenarios. PDSEs Extended Sharing allows writing multiple members at the same time, while ELIBs allow only one update at a time. This can make a difference when Concurrent Action Processing is used.

Disadvantages of PDSEs:

• Limited to a single volume
• Limited to 522,239 members

 

Advantages of ELIBs:

• Automatic space reuse
• Automatic directory expansion, although manual adjustment can improve performance
• VSAM ELIBs can be multivolume. PDSs and PDSEs are limited to 1 volume.
• VSAM ELIBs can grow to 123 extents per each volume
• No limit on number of members
• ELIBs can store 10 character member names. This is useful if you have some 9-10 characters long element names.
• Automatic member data compression, reducing DASD consumption. However, depending on settings, PDSE member data can also be compressed when the PDSE is used as an Endevor base, delta or listing library.

Disadvantages of ELIBs:

• Depending on usage patterns, free space can get fragmented and in some extreme situations, adding a large member can fail.
• Only accessible using Endevor. For example, you cannot browse ELIB members directly in ISPF and compilers cannot read ELIB members directly either.