ZFileRecordReader (IBM JZOS Toolkit API)

java.lang.Object
- com.ibm.jzos.RecordReader
- - com.ibm.jzos.ZFileRecordReader

All Implemented Interfaces:

ZFileConstants
```
public class ZFileRecordReader
extends RecordReader
implements ZFileConstants
```
This ZFile wrapper is no longer the most efficient way to read dataset records. Please see RecordReader.
In order to provide more efficient dataset record mode read performance, it is often beneficial to read a block, rather than a record, at a time from the underlying dataset. This class wraps an instance of ZFile, re-opens it with RECFM=U, and provides an interface for reading a record at a time. The underlying ZFile must have been opened with the following options:
- type=record
- read mode, either text or binary ("r", "rb" or "rt")
Reading the dataset a block at a time limits the number of calls to the C library fread() function and also reduces the number of JNI calls that need to be made. The z/OS XL C/C++ Programming Guide SC09-4765 (Chapter 34 - I/O Performance considerations) recommends taking this approach to increase performance when possible.
All record formats are supported, however performance gains will only be realized when the average record lengths are significantly less than the average block size.
Since:

2.3.0

See Also:

RecordReader

Field Summary
- Fields inherited from interface com.ibm.jzos.ZFileConstants
  DEFAULT_EBCDIC_CODE_PAGE, DEVICE_DISK, DEVICE_DUMMY, DEVICE_HFS, DEVICE_HIPERSPACE, DEVICE_MEMORY, DEVICE_MSGFILE, DEVICE_OTHER, DEVICE_PRINTER, DEVICE_TAPE, DEVICE_TDQ, DEVICE_TERMINAL, DSORG_CONCAT, DSORG_HFS, DSORG_HIPER, DSORG_MEM, DSORG_PDS_DIR, DSORG_PDS_MEM, DSORG_PDSE, DSORG_PO, DSORG_PS, DSORG_TEMP, DSORG_VSAM, ERRNO_E_ABEND, ERRNO_E_DEFINEFILE, ERRNO_E_READERR, ERRNO_E_WRITEERR, ERRNO_EACCES, ERRNO_EILSEQ, ERRNO_EINVAL, ERRNO_EIO, ERRNO_EPERM, FLAG_DISP_MOD, FLAG_DISP_OLD, FLAG_DISP_SHR, FLAG_PDS_ENQ, LAST_OP_BSAM_BLDL, LAST_OP_BSAM_CLOSE, LAST_OP_BSAM_CLOSE_T, LAST_OP_BSAM_NOTE, LAST_OP_BSAM_OPEN, LAST_OP_BSAM_POINT, LAST_OP_BSAM_READ, LAST_OP_BSAM_STOW, LAST_OP_BSAM_WRITE, LAST_OP_C_CANNOT_EXTEND, LAST_OP_C_DBCS_SI_TRUNCATE, LAST_OP_C_DBCS_SO_TRUNCATE, LAST_OP_C_DBCS_TRUNCATE, LAST_OP_C_DBCS_UNEVEN, LAST_OP_C_FCBCHECK, LAST_OP_C_TRUNCATE, LAST_OP_HSP_CREATE, LAST_OP_HSP_DELETE, LAST_OP_HSP_EXTEND, LAST_OP_HSP_READ, LAST_OP_HSP_WRITE, LAST_OP_IO_CATALOG, LAST_OP_IO_DEVTYPE, LAST_OP_IO_LOCATE, LAST_OP_IO_OBTAIN, LAST_OP_IO_RDJFCB, LAST_OP_IO_RENAME, LAST_OP_IO_SCRATCH, LAST_OP_IO_SWAREQ, LAST_OP_IO_TRKCALC, LAST_OP_IO_UNCATALOG, LAST_OP_QSAM_FREEPOOL, LAST_OP_QSAM_GET, LAST_OP_QSAM_PUT, LAST_OP_QSAM_RELSE, LAST_OP_QSAM_TRUNC, LAST_OP_SVC99_ALLOC, LAST_OP_SVC99_ALLOC_NEW, LAST_OP_SVC99_UNALLOC, LAST_OP_TGET_READ, LAST_OP_TGET_WRITE, LAST_OP_VSAM_CLOSE, LAST_OP_VSAM_ENDREQ, LAST_OP_VSAM_ERASE, LAST_OP_VSAM_GENCB, LAST_OP_VSAM_GET, LAST_OP_VSAM_MODCB, LAST_OP_VSAM_OPEN_ESDS, LAST_OP_VSAM_OPEN_ESDS_PATH, LAST_OP_VSAM_OPEN_FAIL, LAST_OP_VSAM_OPEN_KSDS, LAST_OP_VSAM_OPEN_KSDS_PATH, LAST_OP_VSAM_OPEN_RRDS, LAST_OP_VSAM_POINT, LAST_OP_VSAM_PUT, LAST_OP_VSAM_SHOWCB, LAST_OP_VSAM_TESTCB, LOCATE_KEY_EQ, LOCATE_KEY_EQ_BWD, LOCATE_KEY_FIRST, LOCATE_KEY_GE, LOCATE_KEY_LAST, LOCATE_RBA_EQ, LOCATE_RBA_EQ_BWD, MODE_FLAG_APPEND, MODE_FLAG_READ, MODE_FLAG_UPDATE, MODE_FLAG_WRITE, OPEN_MODE_BINARY, OPEN_MODE_RECORD, OPEN_MODE_TEXT, RECFM_A, RECFM_B, RECFM_F, RECFM_M, RECFM_S, RECFM_U, RECFM_V, S_IRGRP, S_IROTH, S_IRUSR, S_IRWXG, S_IRWXO, S_IRWXU, S_ISGID, S_ISUID, S_ISVTX, S_IWGRP, S_IWOTH, S_IWUSR, S_IXGRP, S_IXOTH, S_IXUSR, SEEK_CUR, SEEK_END, SEEK_SET, VSAM_TYPE_ESDS, VSAM_TYPE_ESDS_PATH, VSAM_TYPE_KSDS, VSAM_TYPE_KSDS_PATH, VSAM_TYPE_NOTVSAM, VSAM_TYPE_RRDS

Method Summary

All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`void`	`close()` Close the reader and underlying ZFile.
`int`	`getBlksize()` Answer the BLKSIZE, which is the maximum block length supported by the dataset.
`java.lang.String`	`getDDName()` Answers the DD name used to open the underlying dataset.
`java.lang.String`	`getDsn()` Answers the native dataset's absolute name, or name(member) if the native dataset is a member of a PDS.
`int`	`getLrecl()` Answer the LRECL, which is the maximum record length for variable length files.
`java.lang.String`	`getRecfm()` Get the native file's record format.
`int`	`getRecfmBits()` Answer the RECFM bits
`static ZFileRecordReader`	`newReader(ZFile zFile)` Deprecated. This method no longer provides the most efficient way to perform dataset I/O.
`int`	`read(byte[] buf)` Read a record from the native file into a buffer.
`int`	`read(byte[] buf, int offset, int len)` Read a record from the native file into a buffer.

Methods inherited from class com.ibm.jzos.RecordReader
getAutoFree, newReader, newReaderForDD, setAutoFree

Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Method Detail
  - newReader
```
@Deprecated
public static ZFileRecordReader newReader(ZFile zFile)
                                               throws ZFileException
```
    Deprecated. This method no longer provides the most efficient way to perform dataset I/O.
    
    Construct a new ZFileRecordReader on the given ZFile, which must have been opened in read, record mode.
    
    Throws:
    
    ZFileException
    
    See Also:
    
    RecordReader.newReader(String, int), RecordReader.newReaderForDD(String)
  - read
```
public int read(byte[] buf)
         throws ZFileException
```
    Read a record from the native file into a buffer.
    
    Specified by:
    
    read in class RecordReader
    
    Parameters:
    
    buf - the byte array into which the bytes will be read
    
    Returns:
    
    the number of bytes read, -1 if EOF encountered.
    
    Throws:
    
    ZFileException - if the native call fails
  - read
```
public int read(byte[] buf,
                int offset,
                int len)
         throws ZFileException
```
    Read a record from the native file into a buffer.
    
    Specified by:
    
    read in class RecordReader
    
    Parameters:
    
    buf - the byte array into which the bytes will be read
    
    offset - the offset, inclusive in buf to start reading bytes
    
    len - the number of bytes to read
    
    Returns:
    
    the number of bytes read, -1 if EOF encountered.
    
    Throws:
    
    ZFileException - if the native call fails
  - close
```
public void close()
           throws ZFileException
```
    Close the reader and underlying ZFile.
    
    Specified by:
    
    close in class RecordReader
    
    Throws:
    
    ZFileException - if the native call fails
  - getBlksize
```
public int getBlksize()
```
    Description copied from class: RecordReader
    
    Answer the BLKSIZE, which is the maximum block length supported by the dataset.
    
    Specified by:
    
    getBlksize in class RecordReader
  - getDDName
```
public java.lang.String getDDName()
```
    Answers the DD name used to open the underlying dataset. Returns null unless this instance was created by RecordReader.newReaderForDD(String)
    
    Specified by:
    
    getDDName in class RecordReader
    
    Returns:
    
    String ddname
  - getDsn
```
public java.lang.String getDsn()
```
    Description copied from class: RecordReader
    
    Answers the native dataset's absolute name, or name(member) if the native dataset is a member of a PDS.
    
    Specified by:
    
    getDsn in class RecordReader
    
    Returns:
    
    String dataset name
  - getLrecl
```
public int getLrecl()
```
    Description copied from class: RecordReader
    
    Answer the LRECL, which is the maximum record length for variable length files.
    
    Specified by:
    
    getLrecl in class RecordReader
  - getRecfm
```
public java.lang.String getRecfm()
```
    Description copied from class: RecordReader
    
    Get the native file's record format.
    
    Specified by:
    
    getRecfm in class RecordReader
    
    See Also:
    
    ZFile.getRecfm()
  - getRecfmBits
```
public int getRecfmBits()
```
    Description copied from class: RecordReader
    
    Answer the RECFM bits
    
    Specified by:
    
    getRecfmBits in class RecordReader
    
    See Also:
    
    ZFile.getRecfmBits()

Fields inherited from interface com.ibm.jzos.ZFileConstants

Methods inherited from class com.ibm.jzos.RecordReader

Methods inherited from class java.lang.Object

newReader

read

read

close

getBlksize

getDDName

getDsn

getLrecl

getRecfm

getRecfmBits