could not allocate multiple data sets via one script

[tangthth]

Issue Description:

vsam.allocSync() could not allocate multiple data sets via one single nodejs script.
No such problem for vsam.openSync(), which could open multiple data sets via one single script.

Reproduce Steps:

1. write a nodejs script below to allocate 2 data sets
2. execute the script

Logs:

/u/usra/myscripts:>node test_vsam.js
New vsam dataset allocated: USRA.NODEJSD.VSAMDSA1
/u/usra/workdir/nodejs/nodejs.test.vsam_1.0.0/scripts/test_vsam.j
s:333
vsamObjb = vsam.allocSync(dsnameb, JSON.parse(fs.readFileSync('schema.json')
))
¬
TypeError: Failed to allocate dataset
at TypeError (native)
at vsamAllocateX (/u/usra/workdir/nodejs/nodejs.test.vsam_1.0
.0/scripts/test_vsam.js:333:21)
at Object. (/u/usra/workdir/nodejs/nodejs.test.vsa
m_1.0.0/scripts/test_vsam.js:347:1)
at Module._compile (module.js:577:32)
at Object.Module._extensions..js (module.js:586:10)
at Module.load (module.js:494:32)
at tryModuleLoad (module.js:453:12)

Reference:

    vsamObja = vsam.allocSync(dsnamea, JSON.parse(fs.readFileSync('schema.json')))
    console.log("New vsam dataset allocated: " + dsnamea)
    vsamObjb = vsam.allocSync(dsnameb, JSON.parse(fs.readFileSync('schema.json')))	
    console.log("New vsam dataset allocated: " + dsnameb)